Respirators

Tuesday, September 9, 2008

A respirator is a device designed to protect the wearer from inhaling harmful dusts, fumes, vapors, and/or gases. Respirators come in a wide range of types and sizes used by the military, private industry, and the public. Respirators range from cheaper, single-use, disposable masks to reusable models with replaceable cartridges.

There are two main categories: the air-purifying respirator, which forces contaminated air through a filtering element, and the air-supplied respirator, in which an alternate supply of fresh air is delivered. Within each category, different techniques are employed to reduce or eliminate noxious airborne contents.

Early development of respirators

The history of protective respiratory equipment can be traced back as far as the 16th century, when Leonardo da Vinci suggested that a finely-woven cloth dipped in water could protect sailors from a toxic weapon made of powder that he had designed. [1] Alexander von Humboldt introduced a primitive respirator in 1799 when he was working in Prussia as a mining engineer.

Practically all the early respirators consisted of a bag placed completely over the head, fastened around the throat with windows through which the wearer could see. Some were rubber, some were made of rubberized fabric, and still others of impregnated fabric, but in most cases a tank of compressed air or a reservoir of air under slight pressure was carried by the wearer to supply the necessary breathing air. In some devices certain means were provided for the adsorption of carbon dioxide in exhaled air and the rebreathing of the same air many times; in other cases valves were provided for exhalation of used air.

Woodcut of Stenhouse's mask

The first US patent for an air purifying respirator was granted to Lewis P. Haslett in 1848 for his 'Haslett's Lung Protector,' which filtered dust from the air using one-way clapper valves and a filter made of moistened wool or a similar porous substance. Following Haslett, a long string of patents were issued for air purifying devices, including patents for the use of cotton fibers as a filtering medium, for charcoal and lime absorption of poisonous vapors, and for improvements on the eyepiece and eyepiece assembly. Hutson Hurd patented a cup-shaped mask in 1879 that became widespread in industrial use, and Hurd's H.S. Cover Company was still in business in the 1970s.

Inventors were also developing air purifying devices across the Atlantic. John Stenhouse, a Scottish chemist, was investigating the power of charcoal, in its various forms, to capture and hold large volumes of gas. He put his science to work in building one of the first respirators able to remove toxic gases from the air, paving the way for activated charcoal to become the most widely used filter for respirators. British physicist John Tyndall took Stenhouse's mask, added a filter of cotton wool saturated with lime, glycerin, and charcoal, and invented a 'fireman's respirator,' a hood that filtered smoke and gas from air, in 1871; Tyndall exhibited this respirator at a meeting of the Royal Society in London in 1874. Also in 1874, Samuel Barton patented a device that 'permitted respiration in places where the atmosphere is charged with noxious gases, or vapors, smoke, or other impurities.' German Bernhard Loeb patented several inventions to 'purify foul or vitiated air,' and counted among his customers the Brooklyn Fire Department.

Chemical Warfare

The Second Battle of Ypres was the first time Germany used chemical weapons on a large scale on the Western Front in World War I and the first time a colonial force (Canadians) pushed back a major European power (Germans) on European soil, which occurred in the battle of St. Juliaan-Kitcheners' Wood. 168 tons of chlorine gas were released on 22 April over a four mile front. Around 6,000 troops died within ten minutes from asphyxiation. The gas affects the lungs and the eyes causing respiration problems and blindness. Being denser than air it flowed downwards forcing the troops to climb out of trenches.

Eventually reserve Canadian troops held the front, being away from the attack, using urine-soaked cloths as primitive respirators. A Canadian soldier had discovered that the ammonia in urine would react with the chlorine, neutralizing it, and that the water would dissolve the chlorine, allowing the soldiers to breathe through the gas. This is the first recorded response and defense against chemical attacks using respirators.

Modern respirator technology

All respirators have some type of facepiece held to the wearer's head with straps, a cloth harness, or some other method. The facepiece of the respirator covers either the entire face or the bottom half of the face including the nose and mouth. Half-face respirators can only be worn in environments where the contaminants are not toxic to the eyes or facial area. For example, someone who is painting an object with spray paint could wear a half-face respirator, but someone who works with chlorine gas would have to wear a full-face respirator. Facepieces come in many different styles and sizes, to accommodate all types of face shapes, and there are many books and references available for determining which kind of hazard requires what type of respirator.

Air-purifying respirators

Protective filter mask worn by NYPD officer

Air-purifying respirators are used against particulates (such as smoke or fumes), gases, and vapors that are at atmospheric concentrations less than immediately dangerous to life and health. The air-purifying respirator class includes:

• negative-pressure respirators, using mechanical filters and chemical media
• positive-pressure units such as powered air-purifying respirators (PAPRs)
• Escape Only respirators such as Air-Purifying Escape Respirators (APER) for use by the general public for Chemical, Biological, Radiological, and Nuclear (CBRN) terrorism incidents.

Half- or full-facepiece designs of this type are marketed in many varieties depending on the hazard of concern. They use a filter which acts passively on air inhaled by the wearer. Some common examples of this type of respirator are single-use escape hoods and filter masks. The latter are typically simple, light, single-piece, half-face masks and employ the first three mechanical mechanisms in the list below to remove particulates from the air stream. The most common of these is the disposable white N95 variety. The entire unit is discarded after some extended period or a single use, depending on the contaminant. Filter masks also come in replaceable-cartridge, multiple-use models. Typically one or two cartridges attach securely to a mask which has built into it a corresponding number of valves for inhalation and one for exhalation.

Mechanical filter respirators

Mechanical filter respirators retain particulate matter when contaminated air is passed through the filter material. This was the method used by early inventors such as Haslett and Tyndall. Wool is still used today as a filter, along with other substances such as plastic, glass, cellulose, and combinations of two or more of these materials. Since the filters cannot be cleaned and reused and therefore have a limited lifespan, cost and disposability are key factors. Single-use, disposable as well as replaceable cartridge models are common.

Mechanical filters remove contaminants from air in the following ways:

1. by particles which are following a line of flow in the airstream coming within one radius of a fiber and adhering to it, called interception;
2. by larger particles unable to follow the curving contours of the airstream being forced to embed in one of the fibers directly, called impaction; this increases with diminishing fiber separation and higher air flow velocity
3. by an enhancing mechanism called diffusion, which is a result of the collision with gas molecules by the smallest particles, especially those below 100 nm in diameter, which are thereby impeded and delayed in their path through the filter; this effect is similar to Brownian motion and raises the probability that particles will be stopped by either of the two mechanisms above; it becomes dominant at lower air flow velocities
4. by using certain resins, waxes, and plastics as coatings on the filter material to attract particles with an electrostatic charge that holds them on the surface of the filter material;
5. by using gravity and allowing particles to settle into the filter material (this effect is typically negligible); and
6. by using the particles themselves, after the filter has been used, to act as a filter medium for other particles.

Considering only particulates carried on an air stream and a fiber mesh filter, diffusion predominates below the 0.1 μm diameter particle size. Impaction and interception predominate above 0.4 μm. In between, near the 0.3 μm most penetrating particle size (MPPS), diffusion and interception predominate.

For maximum efficiency of particle removal and to decrease resistance to airflow through the filter, particulate filters are designed to keep the velocity of air passing through the filter medium as low as possible. This is achieved by manipulating the slope and shape of the filter to provide larger surface area.

A substantial advance in mechanical filter technology was the HEPA filter, invented during the Manhattan Project for protection from radioactive particles and later adapted to additional uses. A HEPA filter can remove as much as 99.97% of all airborne particulates with aerodynamic diameter of 0.3 microns or greater. In the United States, the categories below were established by NIOSH to describe particulate filters.

Oil resistance	Rating	Description
Not oil resistant	N95	Filters at least 95% of airborne particles
	N99	Filters at least 99% of airborne particles
	N100	Filters at least 99.97% of airborne particles
Oil Resistant	R95	Filters at least 95% of airborne particles
	R99*	Filters at least 99% of airborne particles
	R100*	Filters at least 99.97% of airborne particles
Oil Proof	P95	Filters at least 95% of airborne particles
	P99*	Filters at least 99% of airborne particles
	P100	Filters at least 99.97% of airborne particles
*No NIOSH approvals are held by this type of disposable particulate respirator.

Chemical cartridge respirators

Chemical cartridge respirators use a cartridge to remove gases, volatile organic compounds (VOCs), and other vapors from breathing air by adsorption, absorption, or chemisorption. A typical organic vapor respirator cartridge is a metal or plastic case containing from 25 to 40 grams of sorption media such as activated charcoal or or certain resins. The service life of the cartridge varies based, among other variables, on the carbon weight and molecular weight of the vapor and the cartridge media, the concentration of vapor in the atmosphere, the relative humidity of the atmosphere, and the breathing rate of the respirator wearer. When filter cartridges become saturated or particulate accumulation within them begins to restrict air flow, they must be changed.

Powered air-purifying respirators

The purpose of this type of respirator is to take air that is contaminated with one or more types of pollutants, remove a sufficient quantity of those pollutants and then supply the air to the user. There are different units for different environments. The units consist of a powered fan which forces incoming air through one or more filters for delivery to the user for breathing. The fan and filters may be carried by the user or with some units the air is fed to the user via tubing while the fan and filters are remotely mounted.

The type of filtering must be matched to the contaminants that need to be removed. Some respirators are designed to remove fine particulate matter such as the dust created during various woodworking processes. They are not suitable when working with volatile organic compounds such as those used in many spray paints. At the same time filters that are suitable for volatile substances must typically have their filter elements replaced more often than a particulate filter. In addition there is some confusion over terminology. Some literature and users will refer to a particulate filtering unit as a dust mask or filter and then use the term respirator to mean a unit that can handle organic solvents.

Self-contained breathing apparatus

An SCBA typically has three main components: a high-pressure tank (e.g., 2200 psi to 4500 psi), a pressure regulator, and an inhalation connection (mouthpiece, mouth mask or face mask), connected together and mounted to a carrying frame. There are two kinds of SCBA: open circuit and closed circuit.

Open-circuit industrial breathing sets are filled with filtered, compressed air, the same air we breathe normally. The compressed air passes through a regulator, is inhaled by the user, then exhaled out of the system, quickly depleting the supply of air. Most modern SCBAs are open-circuit. An open-circuit SCBA has a full-face mask, regulator, air cylinder, cylinder pressure gauge, and a harness with adjustable shoulder straps and waist belt which lets it be worn on the back. Air cylinders are made of aluminum, steel, or of a composite construction (usually fiberglass-wrapped aluminum.) Commonly an SCBA will be of the "positive pressure" type, which supplies a slight steady stream of air to stop toxic fumes or smoke from leaking into the mask. Not all SCBAs are positive pressure; others are of the "demand" type, which only supply air on demand (i.e., when the regulator senses the user inhaling). All fire departments and those working in toxic environments need to use the positive pressure SCBA for safety reasons.

The closed-circuit type filters, supplements, and recirculates exhaled gas: see rebreather for more information. It is used when a longer-duration supply of breathing gas is needed, such as in mine rescue and in long tunnels, and going through passages too narrow for a big open-circuit air cylinder.

Sandblasting

Sandblasting or bead blasting is a generic term for the process of smoothing, shaping and cleaning a hard surface by forcing solid particles across that surface at high speeds; the effect is similar to that of using sandpaper, but provides a more even finish with no problems at corners or crannies. Sandblasting can occur naturally, usually as a result of particles blown by wind causing eolian erosion, or artificially, using compressed air. An artificial sandblasting process was patented by Benjamin Chew Tilghman on October 18, 1870.

Historically, the material used for artificial sandblasting was sand that had been sieved to a uniform size. The silica dust produced in the sandblasting process caused silicosis after sustained inhalation of dust. Several countries and territories now regulate sandblasting such that it may only be performed in a controlled environment using ventilation, protective clothing and breathing air supply (as shown in the top image).

Other materials for sandblasting have been developed to be used instead of sand; for example, carborundum grit, steel shots, copper slag, powdered slag, glass beads (bead blasting), metal pellets, dry ice, garnet^[1], powdered abrasives of various grades, and even ground coconut shells, corncobs, walnut shells, and baking soda (sodablasting) have been used for specific applications and can produce distinct surface finishes. Some commercial grade blasters are specially designed to handle multiple blast abrasives. These blasters are commonly referred as multi-media blasters.

Sandblasting can also be used to produce three dimensional signage. This type of signage is considered to be a higher end product as compared to the flat signs. These signs often incorporate gold leaf overlay and sometimes crushed glass backgrounds which is called smalts.

Sandblasting can be used to refurbish buildings or create works of art (carved or frosted glass). Modern masks and resists facilitate this process, producing accurate results.

Sandblasting technique is used for cleaning boat hulls, bricks, and concrete work. Sandblasting which is also known as blast cleaning is used for cleaning industrial as well as commercial structures.

Confined Space

A confined space is any space: 1) that has limited or restricted means of entry or exit; 2) is large enough for a person to enter to perform tasks, and 3) is not designed or configured for continuous occupancy. ^[1] A utility tunnel, the inside of a boiler (only accessible when the boiler is off), the inside of a fluid storage tank, a septic tank that has contained sewage, and a small underground electrical vault are all examples of confined spaces. The exact definition of a confined space varies depending on the type of industry. That is, confined spaces on a construction site are defined differently than confined spaces in a paper mill. Confined spaces that present special hazards to workers, including risks of toxic or asphyxiant gas accumulation, fires, falls, flooding, and entrapment may be classified as permit-required confined spaces depending on the nature and severity of the hazard.

In the U.S., entry into permit-required confined spaces must comply with regulations promulgated by the Occupational Safety and Health Administration. These regulations include developing a written program, issuing entry permits, assigning attendant(s), designating entrants, and ensuring a means of rescue.

According to Occupational Safety and Health Administration a permit-required confined space (permit space) has the three characteristics listed above (which define a confined space) and one or more of the following:

1. Contains or has the potential to contain a hazardous atmosphere
2. Contains a material that has the potential for engulfing the entrant
3. Has an internal configuration that might cause an entrant to be trapped or asphyxiated by inwardly converging walls or by a floor that slopes downward and tapers to a smaller cross section
4. Contains any other recognized serious safety or health hazards.

In addition to the hazards posed by the design of the space, work activities can also pose serious safety hazards (heat, noise, vapors, etc.) that must be taken into account when identifying safety measures that must be taken.

Entry certification

In many situations, certification of non-hazardous atmosphere by a trained or competent person is required before personnel may enter a confined space without the use of a respirator. In the United States Navy, that person is the designated shipboard gas-free engineer. Certification in civilian settings can be performed by an Entry Supervisor who, under O.S.H.A. regulations is designated by the employer and ensures that the space is safe to enter and all hazards are controlled.

In the United States, agricultural and construction operations are exempted from regulations governing permit-required confined spaces (which is specific to general industry), but they are still required to identify and control confined space hazards.

Injuries/Fatalities

Injuries and fatalities involving confined spaces are frequent and often involve successive fatalities when would-be rescuers succumb to the same problem as the initial victim. One example was in 2006 at the decommissioned Sullivan Mine in British Columbia, Canada when one initial victim and then three rescuers all died.

According to data collected by the U.S. Department of Labor, Bureau of Labor Statistics, Census of Fatal Occupational Injuries program, fatal injuries in confined spaces fluctuated from a low of 81 in 1998 to a high of 100 in 2000 during the five-year period, averaging 92 fatalities per year.^[2]

Hazard symbol

Wednesday, September 3, 2008

Hazard symbols are easily recognizable symbols designed to warn about hazardous materials or locations. The use of hazard symbols is often regulated by law and directed by standards organizations. Hazard symbols may appear with different colors, backgrounds, borders and supplemental information in order to signify the type of hazard.

Common hazard symbols

Name	Symbol	Unicode	Image
Toxic sign	☠	U+2620
Caution sign	☡	U+2621
Radiation sign	☢	U+2622
Ionizing radiation sign	?	?
Non-ionizing radiation sign	?	?
Biohazard sign	☣	U+2623
Warning sign	⚠	U+26A0
High voltage sign	⚡	U+26A1
Chemical weapon symbol (U.S. Army)[1]	N/A	N/A
Laser hazard sign	?	?
Optical radiation	?	?

More hazard signs can be found on the list of DIN 4844-2 warning signs

Radioactive sign

The international radiation symbol (also known as trefoil) first appeared in 1946, at the University of California, Berkeley Radiation Laboratory. At the time, it was rendered as magenta, and was set on a blue background.^[2] (See right.) The modern version is reddish-purple against a yellow background, and it is drawn with a central circle of radius R, an internal radius of 1.5R and an external radius of 5R for the blades, which are separated from each other by 60°.^[3]

On February 15, 2007, the IAEA and the ISO announced this new ionizing radiation symbol to supplement the traditional trefoil symbol. The new symbol is aimed at alerting anyone, anywhere to the potential dangers of being close to a large source of ionizing radiation.^[4] Experts have felt that the trefoil symbol had little intuitive value and was less likely to be recognized by those not educated in its significance. According to the IAEA, in a survey conducted at an international school, many children mistook the trefoil for a non-threatening propeller. Hence, the Agency, along with the International Organization for Standardization has devised this symbol for sealed radiation sources. It depicts, on a red background, a black colored trefoil radiating waves, a skull and crossbones and a person running away from the scene. The radiating trefoil suggests the presence of radiation and the red background, skull and crossbones warn of the danger. More importantly, the person running away from the scene suggests the action of avoiding the labeled material. The symbol had been tested in 11 countries with different population groups, age and educational background to ensure that it clearly conveys the message “Danger- Stay away”. The new symbol is to be displayed prominently on the device that actually houses the radiation sources, so that, even by mistake, if some one attempts to disassemble the device it provides an explicit warning not to proceed any further.^[5]

Biohazard sign

According to Charles Baldwin, an environmental-health engineer who contributed to its development:

“

We wanted something that was memorable but meaningless, so we could educate people as to what it means.

”

Drawing

All parts of the Biohazard sign can be drawn with a compass and straightedge. The basic outline of the symbol is a plain trefoil, which is three circles overlapping each other equally like in a triple venn diagram with the overlapping parts erased. The diameter of the overlapping part is equal to half the radius of the three circles. Then three inner circles are drawn in with 2/3 radius of the original circles so that it's little tangent to the outside three overlapping circles. A tiny circle in center has a diameter 1/2 of the radius of the three inner circle, and arcs are erased at 90°, 210°, 330°. The arcs of the inner circles and the tiny circle are connected by a line. Finally, the ring under is drawn from the distance to the perimeter of the equilateral triangle that forms between the centers of the three intersecting circles. An outer circle of the ring under is drawn and finally enclosed with the arcs from the center of the inner circles with a shorter radius from the inner circles.^[3]

Toxic sign

The skull-and-crossbones symbol, consisting of a human skull and two bones crossed together under the skull, is today generally used as a warning of danger, particularly in regard to poisonous substances.

The symbol, or some variation thereof, was also featured on the Jolly Roger, the traditional flag of European and American pirates. It is also used by the Skull and Bones, a secret society at Yale University, and is part of the WHMIS home symbols placed on containers to confirm that the substance inside is dangerous in a way.

In the USA, due to concerns that the skull and bones symbol's association with pirates encourages children to play with toxic materials, the Mr. Yuk symbol is also used to denote poison.

On warning signs, an exclamation mark is often used to draw attention to a warning of danger, hazards and the unexpected. It is normally supplied with a note, as it is a generic term.

Chemical hazard

NFPA 704 standard hazard sticker or placard. See NFPA 704 for details.

European hazard sign, saying highly inflammable (33) - gasoline (1203)

A chemical hazard label is a pictogram applied to containers of dangerous chemical compounds to indicate the specific risk, and thus the required precautions. There are several systems of labels.

The U.S.-based National Fire Protection Association (NFPA) has a standard NFPA 704 using a diamond with four colored sections each with a number indicating severity 0-4 (0 for no hazard, 4 indicates a severe hazard). The red section denotes flammability. The blue section denotes health risks. Yellow represents reactivity (tendency to explode). The white section denotes special hazard information. This label is used primarily in the USA.

In Europe, another standard is used, as fixed in the ADR-Agreement. Vehicles carrying dangerous goods have to be fitted with orange signs, where the lower number identifies the substance, while the upper number is a key for the threat it may pose.

European hazard symbols

These hazard symbols for chemicals are defined in Annex II of Directive 67/548/EEC. A consolidated list with translations into other EU languages can be found in Directive 2001/59/EC (See the links section).

Explosive (E)	Oxidizing agent (O)	Highly flammable (F)	Extremely flammable (F+)
Toxic (T)	Very toxic (T+)	Harmful (Xn)	Irritant (Xi)
Corrosive (C)	Dangerous for the environment (N)

Blister Agents

Because of recent terrorist events many workers have expressed concern about the possibility of a terrorist attack involving blister agents. Blister agents have been used as chemical warfare agents, in World War I (1914-1918) and the Iran-Iraq war (1984-1988). The following frequently asked questions will help workers understand what blister agents are and how they may affect their health and safety.

General Information

What are blister agents?

Blister agents or "vesicants" are chemicals which have severely irritating properties that produce fluid filled pockets on the skin and damage to the eyes, lungs and other mucous membranes. Symptoms of exposure may be immediate or delayed until several hours after exposure.

What are the different forms of blister agents and their properties?

The three major categories of blister agents are: sulfur mustard (H,HD,HT), nitrogen mustard (HN-1, HN-2, HN-3), Lewisite (L), and halogenated oximes (CX). Sulfur mustards are clear to yellow or brown oily liquids with a slight garlic or mustard odor. Although volatility is low, vapors can reach hazardous levels during warm weather. Nitrogen mustards are colorless to yellow, oily liquids with variable odors. Lewisite contains arsenic and is a dark oily liquid with a slight odor of geraniums. Phosgene oxime, one of the most common halogenated oximes, is a colorless solid or liquid, with an intense irritating odor.

Why are we concerned about blister agents as a terrorist’s weapon?

There are large stockpiles of blister agents which, if obtained by terrorists, could be released using bombs, explosives, spray tanks, or rockets.

How long will blister agents persist in the environment?

When exposed to air, blister agents will break down but this may take several days. Nitrogen mustards and Lewisite should break down quickly in soil and water. Sulfur mustards, however, may persist for several days in soil and water. When exposed to air, phosgene oxime is broken down slowly, but in water or soil it is broken down more quickly. See the following table for more information:

Types and Characteristics Chemical Agents

		PERSISTENCE	PERSISTENCE		ENTRANCE
TYPE OF AGENT	SYMBOL	SUMMER	WINTER	RATE OF ACTION	VAPOR/AEROSOL	LIQUID
BLISTER	HD, HN	3 days-1 wk	Weeks	Slow	Eyes, Skin, Lungs	Eyes, Skin
	L, HL	1-3 days	Weeks	Quick	Eyes, Skin, Lungs	Eyes, Skin, Mouth
	CX	Days	Days	Very Quick	Eyes, Lungs, Skin	Eyes, Skin, Mouth

*ARMY FIELD MANUAL NO. 8-10-7. Health Service Support in a Nuclear, Biological, and Chemical Environment.

Health Effects

How do blister agents affect people?

Blister agents burn and blister the skin or any other part of the body they contact. Blister agents (whether as a gas, aerosol, or liquid) enter the body primarily through inhalation and dermal contact. They may act on the eyes, mucous membranes, lungs, and skin. Mustard agent symptoms are delayed - with little or no pain at the time of exposure. In some cases, signs of injury may not appear for several hours or days depending on the concentration. Mustard agents are also suspected carcinogens. Lewisite and phosgene oxime cause immediate, severe pain.

For additional information, see

• Agents, Diseases, and Other Threats (A to Z list). Centers for Disease Control and Prevention (CDC) (2004, February 27).

Controls

How do I protect myself from blister agents?

If you are exposed to a blister agent attack, get away from the impacted area quickly without passing through the contaminated area, if possible. It may be necessary to “shelter-in-place” if you can’t get out of a building or if the nearest place with clean air is indoors.

If available, a good way to protect yourself from a from blister agents is to wear appropriate chemical protective clothing and respiratory protection. However, protective equipment does not always work against blister agents. The effectiveness is determined by the materials of construction, the type and level of exposure, and duration of exposure.

What does it mean to "shelter in place"?

"Shelter in place" means to go indoors, close up the building, and wait for the danger to pass. If you are advised to shelter in place, close all doors and windows; turn off fans, air conditioners, and forced-air heating units that bring in fresh air from the outside; only re-circulate air that is already in the building; move to an inner room or basement; and keep your radio turned to the emergency response network or local news to find out what else you need to do.

For additional information see the Shelter-in-Place Information Center.

What should I do if I have been exposed to a blister agent?

If you have been exposed to a blister agent, remove all clothing immediately and wash with copious amounts of soap and water. Seek emergency medical attention.

Is there any treatment for persons exposed to blister agents?

The military has many publications covering the treatment of personnel who have been exposed to blister agents. Examples are the US Army Medical Research Institute of Chemical Defense (USAMRICD) Medical Management of Chemical Casualties Handbook, Chapter 4, Vesicants and Field Manual 8-285, Treatment of Chemical Agent Casualties and Conventional Military Chemical Injuries, Chapter 4, Blister Agents (Vesicants).

Has the federal government made recommendations to protect worker health?

OSHA has not set occupational exposure levels for exposure to blister agents. However, other government departments and agencies have published existing and proposed standards.

• Summary of Chemical Agent Air Exposure Values Table 1. (2004, August 3), 87 KB PDF, 2 pages.
• Summary of Multi-Media Chemical Agent Toxicity and Exposure Values Table 2. (2004, August 3), 206 KB PDF, 2 pages.
• Lewisite. CDC Emergency Preparedness and Response (2003, December 22). This page includes Fact Sheets, an Emergency Response Card, Medical Management Guidelines, and FAQ's about Lewisite.
• Sulfur Mustard. CDC Emergency Preparedness and Response (2003, December 22). This page includes Fact Sheets, an Emergency Response Card, Medical Management Guidelines, and FAQ's about Sulfur Mustard.
• Nitrogen Mustard. CDC Emergency Preparedness and Response (2003, December 22). This page includes Fact Sheets, Emergency Response Card, Medical Management Guidelines, and FAQ's about Nitrogen Mustard.
• Phosgene Oxime. CDC Emergency Preparedness and Response (2003, December 22). This page includes Fact Sheets, Emergency Response Card, Medical Management Guidelines, and FAQ's about Phosgene Oxime.

First Responders

How should first responders prepare for a release of blister agents?

First responders should consider the possible impact of a release and potential exposure to blister agents and address this in their health and safety plan(HASP). The safety and health plan should include guidelines such as: monitoring, detection, awareness training, personal protective equipment, decontamination, and medical surveillance of acutely exposed workers.

What equipment can first responders use to detect if a blister agent is present?

The variety of devices are available to detect blister agent vapor and liquid. The most portable of the vapor detectors are the M256A1 card or ticket and the Chemical Agent Monitor (CAM). The simplest liquid detectors are the M8 and M9 papers. Direct reading instruments that are available include specialized gas chromatographs (Minicams) and ion mobility spectrometers such as the APD 2000. Since some of these detectors cannot adequately detect the agents at safe airborne levels, users should be trained in regards to the use and limitations of the detectors. Listed below is a table of military detection and monitoring equipment:

Military Detection and Monitoring Equipment

Equipment	Agent	Sensitivity	Time	Cost	Operations/ Maintenance/ Limits	Notes
M-8 Paper	Nerve-G Nerve-VX Mustard-H Liquids only	100-µ drops 100-µ drops 100-µ drops	<=30 sec	$1 per book of 25 sheets	Disposable/ hand-held Dry, undamaged paper has indefinite shelf life	Chemical agent detector paper; 25 sheets/book and 50 booklets/box; potential for false positives.
M-9 Paper	Nerve-G Nerve-VX Mustard-H Liquids only	100-µ drops 100-µ drops 100-µ drops	<=20 sec	$5 per 10-m roll	Disposable/ hand-held 3-year shelf life Carcinogen	Adhesive-backed dispenser roll or books.
M-18A2 Detector Kit	Nerve-GB Nerve-VX Mustard-H, HN, HD, HT Lewisite-L, ED, MD Phosgene-CG Blood-AC Liquid, vapor, aerosol	0.1 mg/m3 0.1 mg/m3 0.5 mg/m3 10.0 mg/m3 12.0 mg/m3 8.0 mg/m3	2—3 min	$360	Disposable tubes Hand-held	25 tests per kit; Detector tubes, detector tickets, and M-8.
M-256A1 Detector Kit	Nerve-G and VX Mustard-HD Lewisite-L Phosgene oxime-CX Blood-AC, CK Vapor or liquid	0.005 mg/m3 0.02 mg/m3 2.0 mg/m3 9.0 mg/m3 3.0 mg/m3 8.0 mg/m3	15 min Series is longer AC--25 min	$140	Disposable/ Hand-held 5-year shelf life	Each kit contains 12 disposable plastic sampler-detectors and M-8 paper.
M-272 Water Test Kit	Nerve-G and VX Mustard-HD Lewisite Hydrogen cyanide	0.02 mg/l 2.0 mg/l 2.0 mg/l 20.0 mg/l	7 min 7 min 7 min 6 min	$189	Portable/ lightweight 5-year shelf life USN, USMC	Used to test raw or treated water; Type I and II detector tubes, eel enzyme detector tickets; Kit conducts 25 tests for each agent.
CAM Chemical Agent Monitor	Nerve-GA, GB, VX Blister-HD and HN Vapor only	0.03 mg/m3 0.1 mg/m3	30 sec <=1 min	$7,500	Hand-held/portable battery operated 6—8 hours continuous use. Maintenance required.	Radioactive source. False alarms to perfume, exhaust paint, additives to diesel fuel.
ICAM Improved Chemical Agent Detector	Nerve-G and V Mustard-HD	0.03 mg/m3 0.1 mg/m3	10 sec 10 sec	$7,500	4.5 pounds Minimal training	Alarm only; False positives common.
ICAM-APD Improved Chemical Agent Detector--Advanced Point Detector	Nerve-G Nerve-V Mustard-H Lewisite-L	0.1 mg/m3 0.04 mg/m3 2.0 mg/m3 2.0 mg/m3	30 sec 30 sec 10 sec 10 sec	$15,000	12 pounds including batteries Low maintenance Minimal training	Audible and visual alarm.
ICAD Miniature Chemical Agent Detector	Nerve-G Mustard-HD Lewisite-C Cyanide-AC, CK Phosgene-CG	0.2—0.5 mg/m3 10 mg/m3 10 mg/m3 50 mg/m3 25 mg/m3	2 min (30 sec for high levels) 2 min 15 sec	$2,800	8 oz pocket-mounted 4 months service No maintenance Minimal training	Audible and visual alarm; Marines; No radioactivity.
M-90 D1A Chemical Agent Detector	Nerve-G, V Mustard Lewisite Blood Vapor only	0.02 mg/m3 0.2 mg/m3 0.8 mg/m3 N/A	10 sec 10 sec 80 sec	$16,000	15 lb. with battery Radioactive source exempt from licensing. Minimal training	Ion mobility spectroscopy and metal conductivity technology can monitor up to 30 chemicals in parallel. Alarm only.
M-8A1 Alarm Automatic Chemical Agent Alarm	Nerve-GA, GB, GD Nerve-VX Mustard-HD Vapor only	0.2 mg/m3 0.4 mg/m3 10 mg/m3	<=2 min <=2 min <=2 min	$2,555	Vehicle battery operated Maintenance required	Radioactive source (license required); Automatic unattended operation; Remote placement.
MM-1 Mobile Mass Spectrometry Gas Chromatograph	20—30 CWA Vapor	<10>2 of surface area	<=45 sec	$300,000 military $100,000 civilian	Heater volatizes surface contaminants.	German "Fuchs" (FOX Recon System/Vehicle)
RSCAAL M-21	Nerve-G Mustard-H Lewisite-L Vapor	90 mg/m3 2,300 mg/m3 500 mg/m3		$110,000	Line-of-sight dependent 10 year shelf life 2-person portable tripod	Passive infrared energy detector 3 miles; Visual/ audible warning from 400 meters
SAW Mini-CAD	Nerve-GB Nerve-GD Mustard-HD Vapor	1.0 mg/m3 0.12 mg/m3 0.6 mg/m3	1 min 1 min 1 min 1 pound No calibration	$5,500	Minimal training Field use	Alarm only; False alarms from gasoline vapor, glass cleaner.
ACADA (XM22)	Nerve-G Mustard-HD Lewisite Vapor	0.1 mg/m3 2 mg/m3 --	30 sec 30 sec --	$8,000	Vehicle mounted, battery powered Radioactive source (license required) Minimal training	Audible alarm; Bargraph display--low, high, very high.
Field Mini-CAMs	Nerve-G, V Mustard-H Lewisite-L	<0.0001>3 <0.003>3 <0.003>3	<5 min <5 min <5>	$34,000	Designed for field industry monitoring (10 lb.) 8 hours training 24 hour/7 day operations	Plug-in modules increase versatility; Threshold lower than AEL.
Viking Spectratrak GC/MS	Nerve-G, V Mustard-HD Many others	<0.0001>3 <0.003>3	<10 min <10>	$100,000	Field use, but 85 pounds Needs 120v AC, helium 40 hours training	Lab quality analysis; Library of 62,000 chemical signatures.
HP 6890 GC with flame photometric detector	Nerve-G, V Mustard-HD Many others	<0.0001>3 <0.0006>3	<10 min <10>	$50,000	Not designed for field use Gas, air, 220v AC 40 hours training	State-of- the-art gas chromatograph; Used by CWC treaty lab.

Reference from National Research Council’s Chemical and Biological Terrorism: Research and Development to Improve Civilian Medical Response.

• Guide for the Selection of Chemical Agent and Toxic Industrial Material Detection Equipment for Emergency First Responders. National Institute of Justice Guide 100-00 (Volumes I and II) (2000, June). This guide for emergency first responders provides information about detecting chemical agents and toxic industrial materials and selecting equipment for different applications. Volume II Appendices B, C, D, E have specific equipment information including manufacturers.
• Chemical and Biological Terrorism: Research and Development to Improve Civilian Medical Response. Institute of Medicine and Board on Environmental Studies and Toxicology Commission on Life Sciences, National Research Council (1999).

What personal protective equipment (PPE) should first responders use?

When an active release is occurring, or the release has stopped but there is no information about the duration of the release or the airborne concentration of nerve agents, don level A protection. The requirement of OSHA’s Hazardous Waste Operations and Emergency Response (HAZWOPER) standard (29 CFR 1910.120(q)) provides additional information for responding to hazardous substance releases, including blister agents.

For additional information see CBRN Personal Protective Equipment Selection Matrix for Emergency Responders - Blister Agents.

Healthcare Workers

How should healthcare workers prepare to respond to a blister agent release?

Healthcare facilities should have a health and safety plan in place that addresses the possibility of receiving patients exposed to blister agents from a terrorism event. The document "OSHA Best Practices for Hospital-Based First Receivers of Victims" contains practical information for developing an emergency management plan and includes victim decontamination, personal protective equipment, and employee training.

How do I decontaminate a patient?

Healthcare professionals should don appropriate gloves and respiratory protection and then remove contaminated clothing from victim and thoroughly wash exposed area with soap and water. Healthcare professionals should also wash hands after removing any protective gloves and any other potentially exposed body surfaces.

Heat Stress

During emergency response activities or recovery operations, workers may be required to work in hot environments, and sometimes for extended periods. Heat stress is a common problem encountered in these types of situations. The following frequently asked questions will help workers understand what heat stress is, how it may affect their health and safety, and how it can be prevented.

Where might I be exposed to heat stress?

Any process or job site that is likely to raise the workers deep core temperature (often listed as higher than 100.4 degrees F (38°C)) raises the risk of heat stress. Operations involving high air temperatures, radiant heat sources, high humidity, direct physical contact with hot objects, or strenuous physical activities have a high potential for inducing heat stress in employees. Indoor operations such as foundries, brick-firing and ceramic plants, glass products facilities, rubber products factories, electrical utilities (particularly boiler rooms), bakeries, confectioneries, commercial kitchens, laundries, food canneries, chemical plants, mining sites, smelters, and steam tunnels are examples of industrial locations where problems can occur. Outdoor operations conducted in hot weather, such as construction, refining, asbestos removal, hazardous waste site activities, and emergency response operations, especially those that require workers to wear semi-permeable or impermeable protective clothing, are also likely to cause heat stress among exposed workers.

Are there additional causal factors for heat stress?

Age, weight, degree of physical fitness, degree of acclimatization, metabolism, dehydration, use of alcohol or drugs, and a variety of medical conditions such as hypertension all affect a person's sensitivity to heat. However, even the type of clothing worn must be considered. Prior heat injury predisposes an individual to additional injury. Individual susceptibility varies. In addition, environmental factors include more than the ambient air temperature. Radiant heat, air movement, conduction, and relative humidity all affect an individual's response to heat.

What kind of heat disorders and health effects are possible and how should they be treated?

Heat Stroke is the most serious heat related disorder and occurs when the body's temperature regulation fails and body temperature rises to critical levels. The condition is caused by a combination of highly variable factors, and its occurrence is difficult to predict. Heat stroke is a medical emergency that may result in death. The primary signs and symptoms of heat stroke are confusion; irrational behavior; loss of consciousness; convulsions; a lack of sweating (usually); hot, dry skin; and an abnormally high body temperature, e.g., a rectal temperature of 41°C (105.8°F). The elevated metabolic temperatures caused by a combination of work load and environmental heat, both of which contribute to heat stroke, are also highly variable and difficult to predict.

If a worker shows signs of possible heat stroke, professional medical treatment should be obtained immediately. The worker should be placed in a shady, cool area and the outer clothing should be removed. The worker's skin should be wetted and air movement around the worker should be increased to improve evaporative cooling until professional methods of cooling are initiated and the seriousness of the condition can be assessed. Fluids should be replaced as soon as possible. The medical outcome of an episode of heat stroke depends on the victim's physical fitness and the timing and effectiveness of first aid treatment.

Regardless of the worker's protests, no employee suspected of being ill from heat stroke should be sent home or left unattended unless a physician has specifically approved such an order.

Heat Exhaustion signs and symptoms are headache, nausea, vertigo, weakness, thirst, and giddiness. Fortunately, this condition responds readily to prompt treatment. Heat exhaustion should not be dismissed lightly. Fainting or heat collapse which is often associated with heat exhaustion. In heat collapse, the brain does not receive enough oxygen because blood pools in the extremities. As a result, the exposed individual may lose consciousness. This reaction is similar to that of heat exhaustion and does not affect the body's heat balance. However, the onset of heat collapse is rapid and unpredictable and can be dangerous especially if workers are operating machinery or controlling an operation that should not be left unattended; moreover, the victim may be injured when he or she faints. Also, the signs and symptoms seen in heat exhaustion are similar to those of heat stroke, a medical emergency. Workers suffering from heat exhaustion should be removed from the hot environment and given fluid replacement. They should also be encouraged to get adequate rest and when possible ice packs should be applied.

Heat Cramps are usually caused by performing hard physical labor in a hot environment. These cramps have been attributed to an electrolyte imbalance caused by sweating. Cramps appear to be caused by the lack of water replenishment. Because sweat is a hypotonic solution (±0.3% NaCl), excess salt can build up in the body if the water lost through sweating is not replaced. Thirst cannot be relied on as a guide to the need for water; instead, water must be taken every 15 to 20 minutes in hot environments. Under extreme conditions, such as working for 6 to 8 hours in heavy protective gear, a loss of sodium may occur. Recent studies have shown that drinking commercially available carbohydrate-electrolyte replacement liquids is effective in minimizing physiological disturbances during recovery.

Heat Rashes are the most common problem in hot work environments where the skin is persistently wetted by unevaporated sweat. Prickly heat is manifested as red papules and usually appears in areas where the clothing is restrictive. As sweating increases, these papules give rise to a prickling sensation. Heat rash papules may become infected if they are not treated. In most cases, heat rashes will disappear when the affected individual returns to a cool environment.

Heat Fatigue is often caused by a lack of acclimatization. A program of acclimatization and training for work in hot environments is advisable. The signs and symptoms of heat fatigue include impaired performance of skilled manual, mental, or vigilance jobs. There is no treatment for heat fatigue except to remove the heat stress before a more serious heat-related condition develops.

What kind of engineering controls can be utilized?

General ventilation dilutes hot air with cooler air (ideally, bringing in cooler outside air) and in is the most cost effective). A permanently installed ventilation system usually can handle large areas or entire buildings. Portable or local exhaust systems may be more effective or practical in smaller areas.

Air treatment/air cooling differs from ventilation because it reduces the temperature of the air by removing the heat (and sometimes humidity) from the air. Air conditioning is a method of air cooling which uses a compressed refrigerant under pressure to remove the heat from the air. This method is expensive to install and operate. An alternative to air conditioning is the use of chillers to circulate unpressurized cool water through heat exchangers over which air from the ventilation system is then passed. Chillers are more efficient in cooler climates or in dry climates where evaporative cooling can be used. Local air cooling can be effective in reducing air temperature in specific areas. Two methods have been used successfully in industrial settings. One type, cool rooms, can be used to enclose a specific workplace or to offer a recovery area near hot jobs. The second type is a portable blower with built-in air chiller. The main advantage of a blower, aside from portability, is minimal set-up time.

Another way to reduce heat stress is to cool the employee by increasing the air flow or convection using fans, etc. in the work area. This is generally only effective as long as the air temperature is less than the worker's skin temperature (usually less than 95 degrees F dry bulb). Changes in air speed can help workers stay cooler by increasing both the convective heat exchange (the exchange between the skin surface and the surrounding air) and the rate of evaporation. This does not actually cool the air so moving air must impact the worker directly to be effective.

Heat conduction blocking methods include insulating the hot surface that generates the heat and changing the surface itself. Simple devices such as shields, can be used to reduce radiant heat, i.e. heat coming from hot surfaces within the worker's line of sight. Polished surfaces make the best barriers, although special glass or metal mesh surfaces can be used if visibility is a problem With some sources of radiation, such as heating pipes, it is possible to use both insulation and surface modifications to achieve a substantial reduction in radiant heat.

What administrative or work practice controls may be used?

Acclimatize workers by exposing them to work in a hot environment for progressively longer periods. NIOSH (1986) suggests that workers who have had previous experience in jobs where heat levels are high enough to produce heat stress may acclimatize with a regimen of 50% exposure on day one, 60% on day two, 80% on day three, and 100% on day four. For new workers who will be similarly exposed, the regimen should be 20% on day one, with a 20% increase in exposure each additional day.

Replace Fluids by providing cool (50°-60°F) water or any cool liquid (except alcoholic beverages) to workers and encourage them to drink small amounts frequently, e.g., one cup every 20 minutes. Ample supplies of liquids should be placed close to the work area. Although some commercial replacement drinks contain salt, this is not necessary for acclimatized individuals because most people add enough salt to their summer diets.

Reduce the physical demands by reducing physical exertion such as excessive lifting, climbing, or digging with heavy objects. Spread the work over more individuals, use relief workers or assign extra workers. Provide external pacing to minimize overexertion.

Provide recovery areas such as air-conditioned enclosures and rooms and provide intermittent rest periods with water breaks.

Reschedule hot jobs for the cooler part of the day, and routine maintenance and repair work in hot areas should be scheduled for the cooler seasons of the year.

Monitor workers who are at risk of heat stress, such as those wearing semi-permeable or impermeable clothing when the temperature exceeds 70°F, while working at high metabolic loads (greater than 500 kcal/hour). Personal monitoring can be done by checking the heart rate, recovery heart rate, oral temperature, or extent of body water loss.

To check the heart rate, count pulse for 30 seconds at the beginning of the rest period. If the heart rate exceeds 110 beats per minute, shorten the next work period by one third and maintain the same rest period.

The recovery heart rate can be checked by comparing the pulse rate taken at 30 seconds (P1) with the pulse rate taken at 2.5 minutes (P3) after the rest break starts. The two pulse rates can be interpreted using the following criteria.

Heart rate recovery pattern

P3

Difference between

P1 and P3
Satisfactory recovery	<90	--
High recovery (Conditions may require further study)	90	10
No recovery (May indicate too much stress)	90	<10

Check oral temperature with a clinical thermometer after work but before the employee drinks water. If the oral temperature taken under the tongue exceeds 37.6°C, shorten the next work cycle by one third.

Measure body water loss by weighing the worker on a scale at the beginning and end of each work day. The worker's weight loss should not exceed 1.5% of total body weight in a work day. If a weight loss exceeding this amount is observed, fluid intake should increase.

Develop a heat stress training program, and incorporate into health and safety plans at least the following components:

• Knowledge of the hazards of heat stress;
• Recognition of predisposing factors, danger signs, and symptoms;
• Awareness of first-aid procedures for, and the potential health effects of, heat stroke;
• Employee responsibilities in avoiding heat stress;
• Dangers of using drugs, including therapeutic ones, and alcohol in hot work environments;
• Use of protective clothing and equipment; and
• Purpose and coverage of environmental and medical surveillance programs and the advantages of worker participation in such programs.

What Personal Protective Equipment is effective in minimizing heat stress?

Reflective clothing, which can vary from aprons and jackets to suits that completely enclose the worker from neck to feet, can reduce the radiant heat reaching the worker. However, since most reflective clothing does not allow air exchange through the garment, the reduction of radiant heat must more than offset the corresponding loss in evaporative cooling. For this reason, reflective clothing should be worn as loosely as possible. In situations where radiant heat is high, auxiliary cooling systems can be used under the reflective clothing.

Auxiliary body cooling Ice vests, though heavy, may accommodate as many as 72 ice packets, which are usually filled with water. Carbon dioxide (dry ice) can also be used as a coolant. The cooling offered by ice packets lasts only 2 to 4 hours at moderate to heavy heat loads, and frequent replacement is necessary. However, ice vests do not tether the worker and thus permit maximum mobility. Cooling with ice is also relatively inexpensive.

Wetted clothing such as terry cloth coveralls or two-piece, whole-body cotton suits are another simple and inexpensive personal cooling technique. It is effective when reflective or other impermeable protective clothing is worn. This approach to auxiliary cooling can be quite effective under conditions of high temperature, good air flow, and low humidity.

Water-cooled garments range from a hood, which cools only the head, to vests and "long johns," which offer partial or complete body cooling. Use of this equipment requires a battery-driven circulating pump, liquid-ice coolant, and a container. Although this system has the advantage of allowing wearer mobility, the weight of the components limits the amount of ice that can be carried and thus reduces the effective use time. The heat transfer rate in liquid cooling systems may limit their use to low-activity jobs; even in such jobs, their service time is only about 20 minutes per pound of cooling ice. To keep outside heat from melting the ice, an outer insulating jacket should be an integral part of these systems.

Circulating air is the most highly effective, as well as the most complicated, personal cooling system. By directing compressed air around the body from a supplied air system, both evaporative and convective cooling are improved. The greatest advantage occurs when circulating air is used with impermeable garments or double cotton overalls. One type, used when respiratory protection is also necessary, forces exhaust air from a supplied-air hood ("bubble hood") around the neck and down inside an impermeable suit. The air then escapes through openings in the suit. Air can also be supplied directly to the suit without using a hood in three ways: by a single inlet, by a distribution tree, or by a perforated vest. In addition, a vortex tube can reduce the temperature of circulating air. The cooled air from this tube can be introduced either under the clothing or into a bubble hood. The use of a vortex tube separates the air stream into a hot and cold stream; these tubes also can be used to supply heat in cold climates. Circulating air, however, is noisy and requires a constant source of compressed air supplied through an attached air hose. This system tethers the worker and limits his or her mobility. Additionally, since the worker feels comfortable, he or she may not realize that it is important to drink liquids frequently.