Gases and Vapors
Gases and vapors may be toxic or inert. Toxic gases and vapors can poison the body either immediately (acute effects) or over a period of time (chronic effects). Inert gases and vapors can displace oxygen, creating an oxygen deficient atmosphere.

Particulates
Particulates may be solids such as dusts, smokes and fumes or liquids like fogs or mists. Such contaminants may be toxic or simply a nuisance.

Oxygen Deficient Areas
Oxygen deficiency occurs mainly in confined areas such as storage bins or sewers where breathable air may be reduced by displacement with other gases or used up by chemical reactions. Air normally contains approximately 21% oxygen by volume. In atmospheres where the concentration is less than 19.5%, you may suffer injury or death.

Any of these hazards can cause injury or death under certain circumstances and they are often found in combination.

Which Respirator?
As part of the fit testing process, Environmental Health personnel should provided the user with specific information about what manufacturer's respirator, model, size, and cartridges he/she is authorized to wear. This combination of equipment is selected to protect the user from the hazards identified in the work environment. It should never be used as protection against any other hazards. If new or unusual hazards are encountered, the user must contact Environmental Health personnel for advice concerning protection from those hazards and not assume that the current selected respirator provides protection. The choice of respiratory protection equipment depends on the characteristics of the hazardous substance, the concentration present, and limitations of the respiratory protection equipment itself.

Respirators can have two general types of fit:

• Tight Fitting - that is, quarter face masks, which cover the mouth and nose; half face masks, which cover the bridge of the nose to the bottom of the chin; and full face masks, which cover the face from the hairline to below the chin.
• Loose Fitting - such as hoods, helmets, or full suits that cover the head completely.

Air Purifying Respirators
An air purifying respirator (APR) cleans the air by filtering particulates, by adsorbing gases and vapors on activated carbon, or by reacting with acid gases to neutralize them.
Air purifying respirators may be half-face or full-face masks using changeable cartridges. These cartridges can be replaced when no longer effective or to protect the user from a different hazard.

APR's operate on the principle of negative pressure. Which means that when the mask is properly fitted to the users face, the pressure inside the mask is below ambient pressure outside the mask.

Included under this category of respirator is the filtering facepiece (dust mask). Both the terms filtering facepiece and dusk mask are used interchangeably by Occupational Safety & Health Administration (OSHA). The difference between a traditional one strap dust mask that is commonly available at any hardware store and the two strap model that OSHA is specifying in the Respiratory Protection Standard is National Institute of Occupational Safety & Health (NIOSH) certification and the two strap model can be fit tested.

OSHA defines a filtering facepiece as negative pressure particulate respirator with a filter that is an integral part of the facepiece or the entire facepiece composed of the filter medium.

Another term that may cause confusion is elastomeric mask/respirator This is simply a traditional silicon or rubber tight fitting quarter, half or full face respirator

NOTE: An APR does not supply breathable air in oxygen deficient areas and should never be used where the concentration of oxygen is less than 19.5%.

Changeable Cartridges and Particulate Filters
Each cartridge is designed to protect user from a specific hazard. The substances a cartridge is designed to protect the user from are written on the side of the cartridge. The cartridge should only be used for protection from these substances. They do not provide protection from any other hazards.
To help identify the hazards each cartridge will protect the user from, they are color coded as follows:

White - Acid Gas
Black - Organic Vapors
Green - Ammonia Gases
Magenta - Radioactive Materials
Orange - Dusts, Fumes, Mists
Yellow - Acid Gas and Organic Vapor

Combination cartridges are available and include the color codes for all hazards from which they provide protection.

Particulate filters can either be the cartridge type used with an elastomeric mask or a filtering facepiece respirator. These filters are given percentage ratings (95, 99 and 99.97) as to their efficiency at capturing a 0.3 micron particle. Filters are now also given designations as to their resistance to oil absorption, N = Not Oil Resistant, R = Oil Resistant and P = Oil Proof. Both of these designation will appear on the label of the filter.

Air Supplied Respirators
Air supplied respirators provide breathable air from a tank or compressor. They are used in areas where the concentration of contaminants is too high to use air purifying respirators or where the oxygen content is too low. There are two kinds of air supplied respirators. A supplied air respirator (SAR) connects to stationary tanks or a compressor. A self-contained breathing apparatus (SCBA) is a portable air supply that can be carried by the worker, usually in a frame strapped to the back.

Respirator Fit Testing
A respirator must fit properly to provide adequate protection. The initial selection and fitting of a respirator must be done under controlled situations. A quantitative fit test is the best available means of ensuring a respirator will protect the user to the degree necessary. This fit test measures particle concentration outside and inside the respirator and calculates the ratio of these numbers to establish a fit factor. This fit factor is compared to fit factors established in respiratory protection standards to determine whether or not a satisfactory fit has been achieved.
Many circumstances may keep the user from getting a satisfactory fit. Facial hair may prevent a good face-to-facepiece seal if between the respirator seal and the skin of the face.

Inspecting the Respirator
The user must inspect his/her respirator before and after each use. Damaged or worn parts make the respirator unsafe and the parts must be replaced before the respirator can be used again.
Check for frayed or worn straps.
Examine the facepiece seal for damage.
Make sure all of the screws are tight.
Check all silicone, rubber, and plastic parts for flexibility or cracks.
Make sure that the inhalation and exhalation valves are clean, flexible, and properly seated.
Ensure the face plate of full-face respirators is clear and in good condition.

Wear and Care of the Respirator
After inspecting and putting on the respirator, the fit must be checked by performing a positive and negative pressure test.

Positive Pressure Test - Cover the exhalation valve and exhale gently into the respirator. If the seal is good, the respirator will inflate slightly and stay inflated. If it settles back onto the users face before the next inhalation, it is leaking.

Negative Pressure Test - Cover the cartridges and inhale slightly. The respirator should collapse and remain collapsed as long as the user maintains the vacuum inside the respirator. If it expands while you are still holding your breath, it is leaking.

If there is leakage during either of these procedures, readjust the straps, reseat the mask on the face, and retest. Do not tighten the straps to the point of being uncomfortable. If the respirator still leaks, contact Environmental Health personnel to be fit tested for another mask.

Warning Signs
Should any of the following occur while using a respirator, leave the area immediately.

Difficulty in breathing.
Tasting or smelling the hazardous substance or anything unrecognized.
Dizziness, coughing, nausea, weakness, or shortness of breath.

It is recommend the user change filter cartridges at least every 20 hours of use, more often if needed.

Cleaning
Respirators should be cleaned after each use with either soap and water or a disposal wipe. In addition to this cleaning, respirators should be disassembled, thoroughly cleaned, and sanitized at least twice a year, more often if used in very dirty environments. This cleaning will prolong the life of the respirator and lessen the chances of constant reinfection if a cold or other virus is contracted. This should be accomplished as follows:

Remove all filters and cartridges. Disassemble the respirator. Wash the respirator in a mild soap solution using a sponge or soft brush. Rinse in clean, warm, running water. A thorough rinse will remove all soap solution which might irritate skin or damage the respirator. To sanitize the respirator, add one tablespoon of household bleach per gallon of water in a sink or container. Immerse the respirator parts in this solution and allow to stand for five minutes. Remove parts, thoroughly rinse under warm, running water. Allow to air dry or blot dry with a clean, lint-free cloth. Before reassembling the respirator, make sure all parts are thoroughly dry. Use this time to inspect the respirator and replace any worn parts.

Storage
Proper storage of a respirator is very important. Before storing, make sure no parts are bent or twisted since storage in this position will cause distortion of the facepiece. Next, seal the respirator in a heavy-duty, resealable plastic bag and store it where it will not be exposed to dust, sunlight, extreme heat or cold, moisture, chemicals, or physical damage. Never hang a respirator by the straps or store it in a contaminated area. Proper storage will ensure the respirator is ready for use and properly functioning the next time it is needed.