RESPIRATORS

Respiratory protection is of primary importance since inhalation is one of the major routes of exposure to chemical toxicants. Respiratory protective devices (respirators) that are suited to atmospheres that are IDLH (Immediately Dangerous to Life or Health) or are likely to become IDLH consist of two types:

• Self-Contained Breathing Apparatus (SCBAs) which supply air from a source carried by the user.

• Supplied-Air Respirators (SARs) which supply air from a source located some distance away and connected to the user by an air-line hose. Supplied-air respirators are sometimes referred to as air-line respirators.

Air-purifying respirators, on the other hand, do not have a separate air source. Instead, they utilize ambient air which is "purified" through a filtering element prior to inhalation. Generally, these are of the negative pressure types.

SCBAs, SARs, and air-purifying respirators are further differentiated by the type of air flow supplied to the facepiece:

Positive-pressure respirators maintain a positive pressure in the facepiece during both inhalation and exhalation. The two main types of positive-pressure respirators are pressure-demand and continuous flow. In pressure-demand respirators, a pressure regulator and an exhalation valve on the mask maintain the mask's positive pressure except during high breathing rates. If a leak develops in a pressure-demand respirator, the regulator sends a continuous flow of clean air into the facepiece, preventing penetration by contaminated ambient air. Continuous flow respirators (including some SARs and all powered air-purifying respirators [PAPRs] send a continuous stream of air into the facepiece at all times. With SARs, the continuous flow of air prevents infiltration by ambient air, but uses the air supply much more rapidly than with pressure-demand respirators. Powered air-purifying respirators [PAPRs] are operated in a positive-pressure continuous-flow mode utilizing filtered ambient air. (However, at maximal breathing rates, a negative pressure may be created in the facepiece of a PAPR.)

Negative-pressure respirators draw air into the facepiece via the negative pressure created by user inhalation. The main disadvantage of negative-pressure respirators is that if any leaks develop in the system (i.e., a crack in the hose or an ill-fitting mask or facepiece), the user draws contaminated air into the facepiece during inhalation.

Federal regulations require the use of respirators that have been tested and approved by MSHA and NIOSH. Testing procedures are described in 30 CFR Part 11. Approval numbers are clearly written on all approved respiratory equipment; however, not all respiratory equipment that is marketed is approved. Periodically, NIOSH publishes a list, entitled NIOSH Certified Equipment List of all approved respirators and respiratory components.

WEARING CONTACT LENSES WITH A RESPIRATOR IN A CONTAMINATED ATMOSPHERE IS PROHIBITED (29 CFR Part 1910.134.

PROTECTION FACTOR:

The level of protection that can be provided by a respirator is indicated by the respirator's protection factor. This number, which is determined experimentally by measuring facepiece seal and exhalation valve leakage, indicates the relative difference in concentrations of substances outside and inside the facepiece that can be maintained by the respirator. For example, the protection factor for full-facepiece air-purifying respirators is 50. This means, theoretically, that workers wearing these respirators should be protected in atmospheres containing chemicals at concentrations that are up to 50 times higher than the appropriate limits. One source of protection factors for various types of atmosphere-supplying (SCBA and SAR) and air-purifying respirators can be found in American National Standards Institute (ANSI) standard ANSI Z88.2-1980.

In situations where the identity and concentration of chemicals in air are known, a respirator should be selected with a protection factor that is sufficiently high to ensure that the wearer will not be exposed to the chemicals above the applicable limits. These limits include the American Conference of Governmental Industrial Hygienists' Threshold Limit Values (TLVs), OSHA's Permissible Exposure Limits (PELs), and the NIOSH Recommended Exposure Limits (RELs) These limits are designed to protect most workers who may be exposed to chemicals day after day throughout their working life. The OSHA PELs are legally enforceable exposure limits, and are the minimum limits of protection that must be met.

It should be remembered that the protection provided by a respirator can be compromised in several situations, most notably:

• If a worker has a high breathing rate
• If the ambient temperature is high or low
• If the worker has a poor facepiece-to-face seal.

At high breathing rates, positive-pressure SCBAs and SARs may not maintain positive pressure for brief periods during peak inhalation. Also, at high work rates, exhalation valves may leak. Consequently, positive-pressure respirators working at high flow rates may offer less protection than when working at normal rates.

A similar reduction in protection may result from high or low ambient temperatures. For example, at high temperatures excessive sweat may cause a break in the face-to-facepiece seal. At very low temperatures, the exhalation valve and regulator may become ice-clogged due to moisture in the breath and air. Likewise, a poor facepiece seal - due to such factors as facial hair, missing teeth, scars, lack of or improper fit testing, etc. - can result in the penetration of air contaminants.

Self-Contained Breathing Apparatus (SCBA):

A self-contained breathing apparatus (SCBA) usually consists of a facepiece connected by a hose and a regulator to an air source (compressed air, compressed oxygen, or an oxygen-generating chemical) carried by the wearer. Only positive-pressure SCBAs are recommended for entry into atmospheres that are immediately dangerous to life and health (IDLH). SCBAs offer protection against most types levels of airborne contaminants. SCBAs are limited by the amount of air carried and its rate of consumption. Also, SCBAs are bulky and heavy, thus they increase the likelihood of heat stress and may impair movement in confined spaces. Generally, only workers handling hazardous materials or operating in contaminated zones require SCBAs.

Escape-only SCBAs are frequently continuous-flow devices with hoods that can be donned to provide immediate emergency protection. Employers should provide and ensure that employees carry and escape SCBA where such emergency protection may be necessary.

As required by MSHA/NIOSH 30 CFR Part 11.80, all compressed breathing gas cylinders must meet minimum U.S. Department of Transportation requirements for interstate shipment. (See also 49 CFR Parts 173 and 178.) All compressed air, compressed oxygen, liquid air, and liquid oxygen used for respiration shall be of high purity and must meet all requirements of OSHA 29 CFR Part 1910.134(d). In addition, breathing air must meet or exceed the requirements of Grade D breathing air as specified in the Compressed Gas Association pamphlet G-7.1 and ANSI Z86.11-1973. Supplied-Air

Supplied-Air Respirators (SARs):

Supplied-air respirators (also known as air-line respirators) supply air, never oxygen, to a facepiece via a supply line from a stationary source. SARs are available in positive-pressure and negative-pressure modes. Pressure-demand SARs with escape provisions provide the highest level of protection (among SARs) and are the only SARs recommended for use at hazardous waste sites. SARs are not recommended for entry into IDLH atmospheres (MSHA/NIOSH 30 CFR Part 11) unless the apparatus is equipped with an escape SCBA.

The air source for supplied-air respirators may be compressed air cylinders or a compressor that purifies and delivers ambient air to the facepiece. SARs suitable for use with compressed air are classified as "Type C" supplied-air respirators as defined in MSHA/NIOSH 30 CFR Part 11. All SAR couplings must be incompatible with the outlets of other gas systems used on site to prevent a worker from connecting to an inappropriate compressed gas source (OSHA 29 CFR 1910.134[d]).

Air-Purifying Respirators:

Air-purifying respirators consist of a facepiece and an air-purifying device, which is either a removable component of the facepiece or an air-purifying apparatus worn on a body harness and attached to the facepiece by a corrugated breathing hose. Air-purifying respirators selectively remove specific airborne contaminants (particulates, gases, vapors, fumes) from ambient air by filtration, absorption, adsorption, or chemical reactions. They are approved for use in atmospheres containing specific chemicals up to designated concentrations, and not for IDLH atmospheres. Air-purifying respirators can be used only when the ambient atmosphere contains sufficient oxygen (19.5 percent) (30 CFR Part 1190[a]).

Conditions that may exclude use of air-purifying respirators:

• Oxygen deficiency.
• IDLH concentrations of specific substances.
• Entry into an unventilated or confined area where the exposure conditions have not been characterized.
• Presence or potential presence of unidentified contaminants.
• Contaminant concentrations are unknown or exceed designated maximum use concentration(s).
• Identified gases or vapors have inadequate warning properties and the sorbent service life is not known and the unit has no end-of-life (ESLI) indicator.
• High relative humidity (may reduce the protection offered by the sorbent).

Air-purifying respirators usually operate only in the negative-pressure mode except for powered air-purifying respirators (PAPRs) which maintain a positive facepiece pressure (except at maximal breathing rates). There are three types of air-purifying devices:

1. Particulate filters
2. Cartridges and canisters, which contain sorbents for specific gases and vapors
3. Combination devices

The efficiencies of these devices vary considerably even for closely related materials.

IMPORTANT NOTE: Respirators must be fit-tested [Fit-tested means that the facepiece seals around the face so that during inhalation negative pressure is formed and air intake is only possible through the cartridge or air hoses]. Face shape and size can vary considerably throughout the human population, therefore it is important that the correct facepiece that fits that particular worker is found and passes the negative pressure test. For more common respirator masks with detachable cartridges, it is easy to fit-test by placing thumbs in the holes where the cartridges attach. In a proper fit-test the mask will cave in on the sides and breathing will become impossible.

Cartridges usually attach directly to the respirator facepiece. Combination canisters and cartridges contain layers of different sorbent materials and remove multiple chemicals or multiple classes of chemicals from the ambient air. Though approved against more than one substance, these canisters and cartridges are tested independently against single substances. Thus, the effectiveness of these canisters against two or more substances has not been demonstrated. Filters may also be combined with cartridges to provide additional protection against particulates. A number of standard cartridges and canisters are commercially available. They are color-coded to indicate the general chemicals or classes of chemicals against which they are effective (29 CFR 1910.134[g]).

MSHA and NIOSH have granted approvals for manufacturers' specific assemblies of air-purifying respirators for a limited number of specific chemicals. Respirators should be used only for those substances for which they have been approved. Use of a sorbent shall not be allowed when there is reason to suspect that it does not provide adequate sorption efficiency against a specific contaminant. In addition, it should be noted that approval testing is performed at a given temperature and over a narrow range of flow rates and relative humidities; thus protection may be compromised in nonstandard conditions. The assembly that has been approved by MSHA and NIOSH to protect against organic vapors is tested against only a single challenge substance, carbon tetrachloride; its effectiveness for protecting against other vapors has not been demonstrated.

Most chemical sorbent canisters are imprinted with an expiration date. They may be used up to that date as long as they were not opened previously. Once opened, they begin to sorb humidity and air contaminants whether or not they are in use. Their efficiency and service life decreases and there fore they should be used immediately. Cartridges should be discarded after use but should not be used for longer than one shift or when breakthrough occurs, whichever comes first. Any cartridges that have been used for short durations only should be stored in a plastic bag to prevent sorption and should not be used longer than the total of one shift.

Where a canister or cartridge is being used against gases or vapors, the appropriate device shall be used only if the chemical(s) have "adequate warning properties" (30 CFR Part 11.150). NIOSH considers a substance to have adequate warning properties when its odor, taste, or irritant effects are detectable and persistent at concentrations below the recommended exposure l imit (REL).

A substance is considered to have poor warning properties when its odor or irritation threshold is above the applicable exposure limit. Warning properties are essential to safe use of air-purifying respirators since they allow detection of contaminant breakthrough, should it occur. While warning properties are not foolproof, because they rely on human senses which vary widely among individuals and in the same individual under varying conditions (e.g., olfactory fatigue), they do provide some indication of possible sorbent exhaustion, poor facepiece fit, or other malfunctions. OSHA permits the use of air-purifying respirators for protection against specific chemicals with poor warning properties provided that:

The service life of the sorbent is known and a safety factor has been applied or The respirator has an approved end-of-sevice-life indicator.

HEALTH AND FITNESS TO WEAR PPE:

• Individuals who are clearly unable to perform based on the medical history and physical exam (e.g., those with severe lung disease, heart disease, or back or orthopedic problems) should be disqualified from wearing respirators.

• Note limitations concerning the worker's ability to use protective equipment (e.g., individuals who must wear contact lenses cannot wear full-facepiece respirators).

• Provide additional testing (e.g., chest X-ray, pulmonary function testing, electrocardiogram) for ability to wear protective equipment where necessary.

• Base the determination on the individual worker's profile (e.g., medical history and physical exam, age, previous exposures and testing).

• Make a written assessment of the worker's capacity to perform while wearing a respirator, if wearing a respirator is a job requirement. Note that the Occupational Safety and Health Administration (OSHA) respirator standard (29 CFR Part 1910.134) states that no employee should be assigned to a task that requires the use of a respirator unless it has been determined that the person is physically able to perform under such conditions.

Training in PPE use is recommended and, for respirators, required by federal regulation in the OSHA standards in 29 CFR Part 1910 Subparts I and Z. http://www.osha-slc.gov/OshStd_toc/OSHA_Std_toc_1910_SUBPART_I.html http://www.osha-slc.gov/OshStd_data/1910_SUBPART_I_APP_B.html http://www.osha-slc.gov/OshStd_toc/OSHA_Std_toc_1910_SUBPART_Z.html

The training portion of the PPE program should delineate the user's responsibilities and explain the following, utilizing both classroom and field training when necessary:

• OSHA requirements as delineated in 29 CFR Part 1910 Subparts I and Z.
• The proper use and maintenance of the selected PPE, including capabilities and limitations.
• The nature of the hazards and the consequences of not using the PPE.
• The human factors influencing PPE performance.
• Instruction in inspecting, donning, checking, fitting, and using PPE.
• Individualized respirator fit testing to ensure proper fit.
• Use of PPE in a test atmosphere to evaluate its effectiveness.
• The user's responsibility (if any) for decontamination, cleaning, maintenance, and repair of PPE.
• Emergency procedures and self-rescue in the event of PPE failure.
• The buddy system.
• The Site Safety Plan and the individual's responsibilities and duties in an emergency.

Levels of PPE protection are delineated by the letters A, B, C and D. Level A is the most stringent and offers the highest available protection of respiratory, skin and eye protection. Level A is also the most difficult to function in. Overprotection is in itself a unnecessary hazard if adequate protection can be met with a lower level of protection. There is a tradeoff between protection level and work efficiency, however, employee safety should be the governing issue when the decision to choose protection levels is made. The following compares the different protection levels:

LEVEL OF PROTECTION	EQUIPMENT
RECOMMENDED: A	- Pressure-demand, full-facepiece of SCBA or pressure-demand supplied-air respirator with escape SCBA. Fully-encapsulating, chemical-resistant suit. Inner chemical-resistant gloves. Chemical-resistant safety boots/shoes. Two-way radio communications. OPTIONAL: Cooling unit, coveralls, Long cotton underwear, Hard hat, Disposable gloves and boot covers.
RECOMMENDED: B	- Pressure-demand, full-facepiece SCBA or pressure-demand supplied-air respirator with escape SCBA. Chemical-resistant clothing [overalls and long-sleeved hooded jacket, one or two piece chemical splash suit, disposable chemical-resistant one-piece suit]. Inner and outer chemical-resistant gloves. Chemical-resistant safety boots/shoes. Hard hat. Two-way radio communications. OPTIONAL: Coveralls, Disposable boot covers, Face shield, Long cotton underwear.
RECOMMENDED: C	- Full-facepiece, air-purifying, canister-equipped respirator. Chemical-resistant clothing [overalls and long-sleeved hooded jacket, one or two piece chemical splash suit, disposable chemical-resistant one-piece suit]. Inner and outer chemical-resistant gloves. Chemical-resistant safety boots/shoes. Hard hat. Two-way radio communications. OPTIONAL: Coveralls, Disposable boot covers, Face shield, Long cotton underwear, Escape Mask.
RECOMMENDED: D	- Coveralls. Safety boots/shoes. Safety glasses or chemical splash goggles. Hard hat. OPTIONAL: Gloves, Escape Mask, Face shield

LEVEL OF PROTECTION	PROTECTION PROVIDED
A	The highest available level of respiratory, skin and eye protection. However, fully-encapsulating suit material must be compatible with the substances involved.
B	The same level of respiratory protection but less skin protection than Level A.
C	The same level of skin protection as Level B, but a lower level of respiratory protection.
D	No respiratory protection. Minimal skin protection.

LEVEL OF PROTECTION	LEVEL OF PROTECTION TO USE WHEN:
A	The chemical substance has been identified and requires the highest level of protection for skin, eyes and the respiratory system based on either: Measured (or potential for) high concentration of atmospheric vapors, gases or particulates. Site operations and work functions involving a high potential for splash, immersion, or exposure to unexpected vapors, gasses, or particulates of materials that are harmful to skin or capable of being absorbed through the intact skin. Substances with a high degree of hazard to the skin are known or suspected to be present and skin contact is possible. Operations must be conducted in confined, poorly ventilated areas until the absence of conditions requiring Level A protection is determined. Atmosphere contains less than 19.5 percent oxygen. Atmosphere is at or above IDLH levels.
B	The type and atmospheric concentration of substances have been identified and require a high level of respiratory protection, but less skin protection than Level A. - Atmospheres with IDLH concentrations of specific substances that do not represent a severe skin hazard. Atmospheres that do not meet the criteria for use of air-purifying respirators. Atmospheres that contain less than 19.5 percent oxygen. Presence of incompletely identified vapors or gases is indicated by direct- reading organic vapor detection instrument, but vapors and gases are not suspected of containing high levels of chemicals harmful to skin or capable of being absorbed through the intact skin.
C	The atmospheric contaminants, liquid splashes or other direct contact will not adversely affect any exposed skin. the types of air contaminants have been identified, concentrations measure and a canister or cartridge is available that can remove the contaminant. All criteria, including fitness testing, for the use of air-purifying respirators are met. The atmosphere contains at least 19.5 percent oxygen.
D	The atmosphere contains no known hazard. - Work functions preclude splashes, immersion, or the potential for unexpected inhalation of or contact with hazardous levels of any chemicals. The atmosphere contains at least 19.5 percent oxygen.

The discomfort and inconvenience of wearing PPE can create a resistance to the conscientious use of PPE. One essential aspect of training is to make the user aware of the need for PPE and to instill motivation for the proper use and maintenance of PPE. http://www.osha-slc.gov/OshStd_toc/OSHA_Std_toc_1910_SUBPART_I.html