OHS Canada Magazine

Know Your Foe

June 10, 2011
By Jason Contant
Health & Safety

Yogi Berra once said, “If you don’t know where you’re going, you’ll end up somewhere else.”

Though known for his wit, Berra’s message regarding the importance of planning is no joking matter, particularly when it comes to occupational health and safety.

In environments where particulates, gases, vapours, fumes and bioaerosols pose a threat, workplace parties who understand the hazards are better equipped to navigate the maze of personal protective equipment (PPE) on the market.

Perhaps no other type of PPE has as extensive offerings as respirators, which can make the search for the right equipment daunting. “People get confused by all the different respirators out there,” says Manish Gupta, market manager for Draeger Safety Canada Ltd., in Mississauga, Ontario. “The contaminants in the workplace, their concentrations and the type of work you do will dictate the type of respirator.”

Sometimes, there is even confusion with regard to specific hazards within the workplace, notes Mackenzie Peters, product line manager, air purifying respirators (APRs), for Mine Safety Appliances Company (MSA) in Pittsburgh. “As a safety manufacturer, we refer these people to safety professionals or industrial hygienists to get a hazard assessment,” Peters says.


Once an assessment has been completed — and sampling data and contaminant information examined — the process of choosing appropriate respiratory protection can begin.


New guidelines from the Canadian Standards Association (CSA) in Mississauga, which could be released by July, are expected to help assemble an accurate picture to ensure worker safety. CSA Z94.4, “Selection, Use and Care of Respirators,” offers a revised flow chart to assist with equipment selection, pictures depicting “interference” issues that may influence sealing surface, and updated fit testing protocols.

Fit testing is essential to ensure the respirator properly seals to the user’s face. Before each use, it is necessary to check the seal by employing either the negative-pressure or the positive-pressure method, notes information from the Infrastructure Health & Safety Association (IHSA) in Mississauga.

The first approach involves putting on the respirator (in line with manufacturer instructions) and adjusting the equipment until it feels snug, but comfortable. Use the hands to block the air inlets, inhale gently and ensure the equipment responds by collapsing slightly, the IHSA advises. The action should not allow any air into the facepiece; if it does, make adjustments and repeat the check until fit is satisfactory.

For the positive-pressure check, cover the exhalation valve instead and exhale gently. The facepiece should puff up, the information notes, but no leakage should occur.


Respirators fall into two main categories: supplied-air respirators (SARs) and APRs. The first type provides clean air through an airline or from a compressed air tank, reports the Canadian Centre for Occupational Health and Safety in Hamilton, Ontario. Gupta says an SAR, such as a self-contained breathing apparatus (SCBA), is best for a “very hazardous environment” where concentrations of gases are high.

CSA Z94.4 also provides some guidance. Section 5.7 addresses atmospheres that are immediately dangerous to life or health (IDLH), citing situations when an SAR should be used: structural firefighting; an untested confined space; an area where a known hazardous contaminant is present at or above published IDLH concentrations or at an unknown concentration; a location where a reduced oxygen concentration may produce a level of hypoxia (a condition in which the body is deprived of adequate oxygen) that is IDLH; and an area where, in the opinion of a qualified person, the condition presents a potential IDLH atmosphere.

Also vital is having a firm grasp of how long air in cylinders will last. “If you have a higher flow of air and adrenaline and you’re working very hard, you can finish up a 30-minute cylinder in less than 15 minutes,” Gupta cautions.

An SCBA, which is an example of an open-circuit system, has a cylinder that offers 30-, 45- and 60-minute options, he says. Inhaled air is drawn from the cylinder and exhaled air is exhausted externally through a valve, Gupta says.

Ray Ellis, vice-president of sales and marketing for Air Systems International, Inc. in Chesapeake, Virginia, says “the best respirator out there to minimize hazards is an SCBA.”

With an open-circuit system, Ellis notes “the nice thing about bottled air is no matter what you walk into, the quality of the air is guaranteed at all times.” The downside is 30-minute cylinders can last less than half that amount of time, with one-hour cylinders often giving between 22 and 27 minutes of air.

To provide a more accurate count on remaining air supply, Ellis reports that some manufacturers have developed a battery-powered, heads-up display that indicates cylinder pressure and estimated run-time based on the user’s breathing pattern.

With a closed-circuit device, Gupta says exhaled air goes back in through the system, carbon dioxide is removed and the user “rebreathes” much of the air that has been cleaned. The advantage of a closed-circuit respirator is that air supply will last for as long as four hours. To provide supplemental air, re-breathers often have oxygen generators.

Ellis says his company has designed a grade-D respiratory filtration device that automatically switches to a back-up air supply source if the main air supply is lost. Lights and alarms signal the time remaining, thereby allowing users to safely “egress the contaminated area, go through decontamination, go to a clean room environment and remove their garments and come out still under respiratory protection,” he says.

Consider workers at the Atlanta-based Centers for Disease Control and Prevention who need to wear high-level hazmat suits and respiratory protection while working in chambers with live viruses like Ebola and AIDS.


The risk of dealing with live viruses is clear, but other workplaces have attracted specific provisions. Consider health care settings, which are expected to get a big protective boost with the planned revisions to CSA Z94.4. A key change includes how to address respirator selection for bioaerosols or infectious diseases, says CSA project manager Ron Meyers. “That’s a key one for the health care industry in terms of dealing with pandemics and what type of respirator do you use for these types of pathogens.”

At the core is a risk assessment of the pathogen. “How serious it is, and what’s the probability of infection? How infectious is it? It’s those things you have to take into account to determine what type of protection you need to wear,” he says.

“When you are dealing with infectious agents, bioaerosols, it’s not like dealing with hazardous chemicals,” he adds. With no established occupational exposure limits for infectious agents and bioaerosols, Myers says officials “had to come up with a brand new approach to dealing with recommending protection levels.”

The CSA was aided in its efforts by accessing expertise and input from the Public Health Agency of Canada in Ottawa. Meyers reports the result was a “control banding method,” based on a risk assessment of the pathogen in question and its severity. When dealing with a deadly pathogen, he says, going through the selection process “could bump you up to a much more protective type of respirator, but in many cases, an N95 is going to be good.”

While an N95 respirator may be appropriate in many health care settings, it may not be the best choice for some other environments. For applications such as welding, spray painting, pulp and paper and asbestos abatement, an APR is likely the safest way to go.

APRs use particulate filters to catch dusts, mists or fumes, chemical cartridges to remove hazardous gases or vapours from the air, or a combination of the two, notes a white paper from MSA. There are also powered air-purifying respirators (PAPRs), which use a motor blower to force ambient air through a filter, with the flow electronically regulated for added comfort. PAPRs offer reduced breathing resistance compared with a nonpowered APR, the paper notes, resulting in less worker stress and fatigue.

Equipment selection must take into account the specific hazards of a workplace. A “general” cartridge may suffice to protect against a family of gases, like organic vapours or acid gases; a gas- or vapour-specific cartridge, such as for mercury, can be used if the particular contaminant is known; or a multi-gas cartridge can cover just about everything.

When it comes to particulate, a P100 filter is popular. It offers 100 per cent particulate protection and is useful in applications like pharmaceutical manufacturing, says Lance Watkins, marketing director for Moldex-Metric, Inc. in Culver City, California.


Choosing appropriate protection need not be confusing if the hazards are known. “In a lot of companies, it’s the same chemicals you deal with all the time,” says Gupta. In one type of workplace, the main issue may be organic vapours; in oil and gas, the biggest issue will almost always be hydrogen sulphide (H2S), he says.

One development that is proving important for the oil and gas sector is an H2S gas cartridge that meets criteria set out by the National Institute for Occupational Safety and Health in Atlanta, Gupta suggests. A couple of manufacturers now have cartridges for coverage of up to 100 parts per million of H2S, contrasting previous offerings typically used in five-minute “escape” respirators, he adds.

“It makes a difference out West, especially in the oil fields,” he says. “Before they had to use supplied air, now they can actually use an air-purifying respirator.”

When trying to determine how effective a cartridge will be, and how long it will last, the MSA’s Mackenzie Peters recommends looking at factors such as temperature, relative humidity and atmospheric pressure.

The CSA standard discusses end-of-life indicators — a feature that lets users know when a cartridge has become contaminated and offers less protection. Myers notes, however, that “a lot of it comes down to manufacturers’ instructions.”


APRs are available in half-mask (covering both the nose and mouth) and full-facepiece formats, says Peters, who adds that the latter option provides a higher protection factor. (There were also quarter-mask APRs, but Gupta suggests these have “gone the way of the dinosaur.”)

Although full facepieces are generally used in environments with skin- and eye-irritating contaminants — such as welding, spraying or grinding applications — users wearing a half-mask will often need some form of personal protection for the eyes, Peters says.

Integrating a full facepiece with other types of PPE has “always been one of the big issues,” Gupta says. “When you are welding and wearing a respirator underneath, now it is getting in the way every time you bring the welding helmet down,” he says by way of example. Some manufacturers have identified a solution: welding adapters that fix onto a full facepiece, allowing the user to wear the helmet and respirator together.

With regard to half-masks, there is a disposable option. Once the cartridges and/or filters are spent, the entire facepiece is discarded and a new facepiece with cartridges/filters used the next time, says Stacy Richardson, a technical service representative for 3M Canada in London, Ontario. “Some organizations like this type of set-up so that they can instruct the users to just throw the entire facepiece and cartridge out at the end of maybe a certain task or project.”

Disposable respirators reduce cleaning and sanitizing demands, as well as ensure the wearer is, in fact, using the correct cartridge or filter, but the option is more expensive and is more limited in the type of cartridge/filter that can be used.

Likewise, there are advantages and disadvantages with reuseable full-facepiece devices. The option may require more education and training around cleaning and maintenance issues, and there is a greater chance of using incorrect cartridges or filters since wearers must replace these. However, there is wider choice in attachments, cartridges, filters or combos.

With comfort in mind, Moldex-Metric’s Lance Watkins says his company offers an “over molded” product that combines respirator parts and, generally, is lighter. “You have less to maintain, less to swap out, less to deal with,” Watkins says.

The company’s single-strap design for particulate respirators also offers “better comfort, longer wear, which ultimately translates to better compliance.”

Whether dealing with deadly viruses or “nuisance” particulates, pairing comfort and compliance can make all the difference to the health and safety of workers.



Stay or go?

Maintenance-free (or disposable) respiratory options still demand care, says Stacy Richardson, technical service representative for 3M Canada in London, Ontario. Although there may not be the need to clean and/or disinfect the products, they must be properly stored to ensure that facepieces remain in good working order, Richardson advises. Consider the following factors when selecting maintenance-free products:

– Would there be greater use of the equipment if it was maintenance-free?
– Since there are usually more available styles of maintenance-free products (all of which still must be fit tested), how many types of respirators does a workplace want in its inventory?
– How often would the user need to change the facepiece or attachments?
– Maintenance-free respirators do not require training on cleaning and maintenance, but users must be trained on how to inspect the facepiece, how to don the respirator and how to conduct seal checks.

News Drop

Whether a half-mask or an N95 particulate respirator, “drop-down” designs are becoming more and more popular, suggests Manish Gupta, market manager for Draeger Safety Canada Ltd. in Mississauga, Ontario. “People have to take breaks, or they have to communicate, or leave an area to go speak to someone,” Gupta points out.

Any and all of these actions requires a worker to take off his respirator, sometimes many times a day. The solution to the repeated donning and doffing may be a drop-down device, which allows the respirator to remain hanging around the user’s neck.

Moldex-Metric, Inc. in Culver City, California offers a drop-down particulate respirator. The respirator features what Lance Watkins, marketing manager for the company, describes as a “kind of a clip-behind-you mechanism that is easier to put on and off.”

While the drop-down concept has garnered support, there is some debate around the issue of which way the respirator should face when it is down, says Gupta.

One school of thought is that the respirator should face outward since there may be “dirt all over your clothing,” which can be transferred to the respirator if it is leaning against the clothing, he says. Others, however, recommend having the respirator face inward to guard against any contaminants in the workplace air.


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