Know Your Foe

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

Though he was 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, national accounts manager for Dräger 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, a product-group manager for Mine Safety Appliances Company (MSA) in Cranberry Township, Pennsylvania. “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.

Fit to be tried

Guidelines from CSA Group can 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, 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.

The right choice

Respirators fall into two main categories: supplied-air respirators (SARs) and air-purifying respirators (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 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 that 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 “re-breathes” 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.

Particular particulate

While an N95 respirator may be appropriate in many healthcare 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 non-powered 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.

A little clarity

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, 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.

Half, full

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.

Regarding 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 setup 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 reusable 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. But there is wider choice in attachments, cartridges, filters or combos.

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

Jason Contant is the former editor of Canadian Occupational Health and Safety News.