Air-purifying respirators

A FITTING SELECTION

By Hayley Chandler

Breathing protection does not end with the purchase of a respirator. In fact, the real work begins with fitting and testing.

Respirators are not like other types of personal protective equipment. They are nothing like a hard hat that buy off the shelf, issue to everyone on the job and wear all the time against the day when a falling brick just might land on your head. In fact, they are the very opposite. When you wear a respirator, it’s because the hazard is there, the air is contaminated and you need protection for every breath you take. It’s not "just in case". It’s for sure.

This means that, if people have to work in a hazardous atmosphere, they will need effective respiratory protection for the whole time that they are exposed to the hazard.

First, you have to choose a respirator that will do the job, that will provide protection against the contaminants in the air. You will need to determine what the contaminant is, whether it is a dust, fume, mist, vapour or gas; and you will have to decide which type of respirator -- supplied air or air-purifying -- is required. (See "The Air You Breathe" January/February 1998, page 44.)

But once you’ve chosen the right type of breathing protection, the job of providing respiratory protection is only just beginning. Next, you have to make sure the respirator fits the person wearing it. Comfort is an issue, and compliance is an issue (people don’t like to wear an uncomfortable device); but, more important, a respirator that doesn’t fit, doesn’t work. If air leaks in around the mask or facepiece, the worker will be inhaling unfiltered air.

Finally, the respirator has to be maintained. If it is damaged or worn out; if the plastic facepiece has become either brittle or too soft; or if the filter is clogged; or if the filtering medium is exhausted, the respirator, again, won’t do its job.

"Respirators are a waste of time and money if steps aren’t taken to make sure that they’re used and used properly," says occupational hygienist Deborah Smith, a consultant in Edmonton, Alta.

Jeff Narver, market supervisor, for occupational health and environmental safety at 3M Canada Company in London, Ont. agrees: "Fit testing is an essential component of any successful respiratory program and anyone who wears a respirator should be fit tested," he says. Almost all manufacturers make facepieces in at least three sizes: small, medium and large. Fit testing helps you choose the right size. It also helps ensure that wearers of tight-fitting elastomeric facepieces can get a proper face-to-facepiece seal. When the facepiece seals tightly against the face, air can only enter the respirator through the filters or chemical-absorbing cartridges and, as a result, it is purified before it enters the wearer’s nose and lungs.

The Canadian Standards Association (CSA) standard Z94.4-93 "Selection, Use, and Care of Respirators" requires that a fit test be used to select the specific make or model of respirator used by each worker. It may be necessary to purchase a variety of sizes, makes and models of respirators to provide a proper fit for a range of workers.

Qualitative and quantitative

There are two categories of fit testing: qualitative and quantitative. The qualitative fit test answers the question, "Is anything getting past the filter." To perform the test, a respirator wearer is exposed to a test chemical, which can be smelled, tasted, or is a respiratory irritant that could cause coughing. The worker uses his or her senses to detect leakage into the facepiece. In other words, workers realize the chemical is entering their respirator and consequently, their respiratory system because they can smell or taste it, or because it is causing physical irritation.

Quantitative fit testing answers the question, "How much is getting through?" It uses electronic instruments to detect leakage by measuring the concentration of a test agent inside and outside the facepiece. "The qualitative tests allow you to determine that the chemical can’t be detected on the inside of the respirator. The quantitative test tells you exactly how much is getting through the respirator and lets you compare it with the concentration that’s on the outside," says occupational hygienist Deborah Smith. Qualitative fit tests are subjective because they depend on the wearer’s senses. Quantitative fit testing is more objective and scientific, but the testing equipment is more expensive. Either type of testing is acceptable.

The CSA standard specifies several protocols for qualitative and quantitative fit testing. All the pieces of head protection workers would normally wear, including hearing, eye and face protection, should be worn during fit tests to ensure that they are compatible with the respirator and do not break the facial seal. The CSA also advises that whenever possible, testing should be performed under conditions that simulate actual work practice. However, fit tests only demonstrate that it is possible for workers to get a good fit. Neither method guarantees that workers will maintain a good fit when they’re working, says Smith.

To ensure they achieve a proper face-to-facepiece seal each time they use their respirators, workers must be able to check the fit themselves. To do this, they must conduct a negative- or positive-pressure check. The first step before either test is to "put your respirator on and wear it for a few minutes so that it warms up a little bit and conforms better to your face," says Narver. For the negative-pressure check, workers should cover the inhalation valves with the palms of their hands and try to inhale. If there is a proper face-to-facepiece seal, this will cause the facepiece to collapse. If there are any leaks, the worker will feel them or hear them, and should reposition or tighten the respirator. For a positive-pressure fit check, workers cover the exhalation valves with their hands and exhale gently. If the respirator puffs up and no air leaks are heard or felt, the respirator fits. "You should do this every time you put a respirator on," says Greg Naherne, a hygienist and occupational health and safety consultant in Hamilton, Ontario.

Inspection and replacement of parts

Fit is not the only thing that workers need to check. "Before each use you should inspect the respirator," says Naherne. Parts that are torn, cracked, worn, broken, or missing must be replaced. A worker wearing a poorly maintained respirator is not getting the necessary protection and has a false sense of security.

"The elastomeric part of the respirator, that is the part that seals with your face, and the valves in the respirator are subject to deterioration after a period of time," says Smith. The respirator should be replaced if the facepiece becomes cracked, torn, distorted or uncomfortable, or if the material the facepiece is made of appears to be breaking down. "There are some chemicals which will eat away at facepieces so they’ll get hard and brittle," says Naherne. The other possibility is that the facepiece will become extremely soft because it has absorbed oils from your skin over a long period of time, adds Narver. Both brittle and extremely soft facepieces need to be replaced.

"Inspect the inhalation and exhalation flaps to make sure they’re not sticking. Sometimes condensed water vapour from your exhalation can cause them to stick open or closed," Naherne says. Make sure there’s no dust or detergent residue on the sealing surfaces of the inhalation or exhalation flaps. Replace missing or defective valve covers. Make sure respirator is clean. Check for any contamination or particles that may interfere with the seal.

The head straps on respirators can loose their elasticity and people compensate by tightening them too much, says Smith. Replace straps that are worn or deteriorated. Check the filter housing for cracks or dents. If the housing becomes misshapen, it becomes difficult to screw the filter in and a little leak can form, she says. "You’ll want to examine the cartridges and make sure they’re screwed on firmly according to the instructions," advises Naherne. Both the filter threads and the housing threads should be inspected for wear.

A low-maintenance respirator has a facepiece with no replaceable parts but does have replaceable cartridges and/or filters. "Cartridge service life is affected by a number of factors," explains Narver, "including the hazard that you’re dealing with, concentration levels, the amount of air that’s drawn through the cartridge, the type of work that you’re doing, and relative humidity in the atmosphere (because humidity is attracted to the charcoal in the cartridge and will exhaust it)."

Storage also affects service life, he says. "You change your cartridges when the breathing resistance increases to the point where it’s becoming uncomfortable if it’s a particulate filter. Or if you can sense the chemical coming through a gas or vapour cartridge," says Smith. Some substances, such as chlorinated hydrocarbon, can start breaking through in a few hours, says Naherne. With other substances, it can be many work shifts before breakthrough occurs. Particulate filters that meet the new National Institute for Occupational Safety and Health (NIOSH) performance criteria (see sidebar on page X) will plug up more quickly because they are more efficient, says Narver.

A simple filtering facepiece respirator has no replaceable parts and should be thrown away when it becomes damaged, when breathing resistance increases or when it gets dirty, particularly if you ever start to see dirt on the inside.

Training requirements

Proper use and care of respirators comes about through careful training. Purchase your respiratory equipment from a supplier who provides training or can help with training. "Every person required to use a respirator shall be trained at least annually," according to the CSA standard. A minimum training program for users is defined by the association as consisting of the following:

* a discussion of the nature, extent, and effects of respiratory hazards to which the person may be exposed;

* an explanation of the operation, limitations, and capabilities of the selected respirator(s);

* instruction in procedures for inspection, putting on and taking off the respirator;

* checking the fit and seals;

* wearing the respirator;

* practical experience to enable the person to become thoroughly familiar and confident with the use of the respirator;

* the procedure for maintenance and storage of the respirator; and

* how to deal with emergency situations involving the use of different respirators or the malfunction of respirators.

In addition to the respirator user, the CSA recommends that the following people also be trained to ensure proper use of respirators:

* the supervisor of workers using respirators;

* the person issuing respirators;

* the person performing fit tests; and

* the person maintaining and repairing respirators.

Clearly, when you purchase respirators, there is much more to consider than the initial cost and selection of the equipment. "There’s a need for an employer to seriously look at the cost of a respirator program," says Naherne. It is very time consuming and expensive to select the proper respirator, to get configurations that fit the faces of your workers, says Smith. Then you have to train your workers, properly maintain the respirators, conduct the necessary fit testing and re-conduct it as needed, and monitor to make sure that workers are actually wearing their respirators properly, she adds. "Often respirators are chosen because it’s thought that to get rid of the hazard is too expensive," she says. "Actually, the use of respirators is terribly expensive if it’s done properly and engineering out the hazard is often cheaper."

Respiratory protection is one area in which "pretty good" isn’t good enough. If respiratory protection is required at all, it has to be part of a program that covers all the bases: equipment selection, proper fitting, training, testing and maintenance. Because if workers don’t use the respirators properly, if they don’t fit, or if they aren’t working properly, you really have no protection at all.

Hayley Chandler is associate editor of safety purchasing for OHS CANADA.

THE NINE NEW CLASSES

Much has been said and written about 42 CFR Part 84 in the last few years. It’s a new American standard for non-powered, particulate removing air-purifying respirators. But what is it, what does it mean, and how does it apply in Canada?

* 42 CFR Part 84 is an American federal health and safety regulation made by OSHA, the Occupational Safety and Health Administration. OSHA is the American agency that makes health and safety regulations (or "rules" as they call them) for the entire United States. Unlike in Canada, where oh&s is primarily a provincial responsibility, OSHA makes the rules for workplaces throughout the United States.

* How does an American law apply in Canada? Well, it doesn’t. Only Canadian federal, provincial and territorial laws and regulations apply here. But 42 CFR Part 84 adopts new standards developed by NIOSH, the National Institute of Occupational Safety and Health. Law makers and regulators around the world look to organizations like NIOSH for "state of the art" information and recommendations on health and safety. OSHA adopted the NIOSH standards for non-powered air-purifying respirators and wrote them into law. Canadian jurisdictions have done the same; so 42 CFR Part 84 does not apply in Canada, but Canadian regulations are based on the same scientific standards.

* NIOSH will address standards governing powered air-purifying respirators and other types of respirators, as well as performance characteristics such as face fit at a later date.

* The new standard was introduced three years ago, and a three-year transition period was set up. That period ends in July of 1998. After that time, only the nine new classes of particulate filtering respirators will have NIOSH approval -- and, consequently, comply with Canadian oh&s regulations.

* Single use dust/mist respirators, replaceable filter dust/mist respirators, dust/mist/fume respirators, radon daughter respirators, pesticide prefilters, and paint spray prefilters have been eliminated. These classes of respirators and filters have been replaced with nine new classes of filters.

* The nine new classes apply only to particulates; these include dusts, mists (tiny droplets of liquid suspended in the air) and fumes (metal that has been vaporized and then condensed into tiny particles of solid metal in the air). It does not apply to gases (such as carbon monoxide or hydrogen sulfide) or to vapours (such as evaporated fuel or solvent). For removing gases and vapours, the previous standards and requirements remain in place unchanged.

* Choosing the right respirator class is actually simpler than it appears. The classes are divided into three series of filters -- N, R and P -- based on whether or not the particulate is an oil-based substance. N series filters (N for Non-oil) can be used for any dust, mist or fume that is not an oil. R series filters (R for oil-Resistant) can be used for up to eight hours in an atmosphere containing a particulate oil or oil-based substance. P series filters (P for oil-Proof) can be used indefinitely in an atmosphere containing oil-based contaminants.

* Each of the three series is further divided into three levels of filter efficiency: 95 per cent, 99 per cent, and 99.97 per cent. The choice of filter efficiency required has to be based on the type of contaminant in the workplace. While the 99.97 per cent efficiency filter might look like the automatic best choice, it may not be the appropriate for removing wood dust, since it would clog up much more quickly.

* Health care professionals should note that all nine classes meet or exceed The Centers for Disease Control and Prevention guidelines for respirator protection against tuberculosis.

You can order the NIOSH User’s Guide to Selection and Use of Particulate Respirators Certified Under 42 CFR Part 84 from NIOSH Public Dissemination, 4676 Columbia Parkway, Cincinnati, Ohio, U.S.A. 45226-1998. Or telephone NIOSH Publications at 513/533-8471 and request NIOSH Publication #96-101. The information can also be downloaded from the NIOSH web site: www.cdc.gov/niosh.

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