Respiratory protection and protective clothing for asbestos

Respirators and protective clothing are the last line of defence in asbestos work, but they are essential in most removal and repair tasks because source controls rarely bring concentrations inside the work area down to safe levels. This lesson explains how asbestos rules specify respirators, how assigned protection factors and maximum use concentrations apply to asbestos, what protective clothing is needed, and how to avoid the common failures that turn good equipment into poor protection. The general principles of respirator programs, selection, medical evaluation, fit testing and maintenance are covered in HSE-240 and are not repeated here.

Why respirators are needed in asbestos work

Even with wetting and careful methods, fibre concentrations close to asbestos removal can far exceed the 0.1 f/cc limit. Dry removal of sprayed fireproofing has been measured at tens to hundreds of fibres per cubic centimetre; wet removal reduces this greatly but often not below the limit. Because asbestos has no known safe level and because concentrations change minute by minute as material is disturbed, asbestos rules require respirators for most work that disturbs asbestos, often regardless of measured concentration.

How Ontario specifies respirators

Ontario's O. Reg. 278/05 specifies respirators by operation type rather than leaving the choice to a calculation. Section 13 sets general requirements (effective face seal, assignment to one worker where practicable, cleaning and inspection after each shift, clean storage), and Table 2 lists the respirators required for each type of work.

BC, Alberta and other provinces specify respirators through their regulations and guidelines, often tied to the risk level and the expected concentration. The common thread is that filtering facepieces (disposable dust masks) are not acceptable for most asbestos work, that 100-series (HEPA-equivalent) filters are the minimum, and that higher-risk work needs full-facepiece, powered or supplied-air respirators.

Protection factors and maximum use concentration

An assigned protection factor (APF) is the level of protection a properly used respirator is expected to provide. The maximum use concentration (MUC) is the highest concentration in which the respirator may be used: the APF multiplied by the exposure limit. For asbestos, with a limit of 0.1 f/cc, the MUC is easy to compute.

LIMIT = 0.1   # f/cc, 8-hour exposure limit

respirators = [
    ("half-facepiece APR, P100",                 10),
    ("loose-fitting PAPR (hood or helmet)",      25),
    ("full-facepiece APR, P100",                 50),
    ("tight-fitting full-facepiece PAPR",      1000),
    ("full-facepiece supplied air, pressure-demand", 1000),
]
for name, apf in respirators:
    print(f"{name:45s} APF {apf:5d}  MUC {apf * LIMIT:6.1f} f/cc")

# Which respirators are adequate for an expected task concentration?
expected = 3.5   # f/cc, illustrative wet removal of sprayed fireproofing
print(f"\nexpected concentration {expected} f/cc needs APF of at least {expected / LIMIT:.0f}")
for name, apf in respirators:
    ok = "adequate" if apf * LIMIT >= expected else "not adequate"
    print(f"  {name:45s} {ok}")

half-facepiece APR, P100                      APF    10  MUC    1.0 f/cc
loose-fitting PAPR (hood or helmet)           APF    25  MUC    2.5 f/cc
full-facepiece APR, P100                      APF    50  MUC    5.0 f/cc
tight-fitting full-facepiece PAPR             APF  1000  MUC  100.0 f/cc
full-facepiece supplied air, pressure-demand  APF  1000  MUC  100.0 f/cc

expected concentration 3.5 f/cc needs APF of at least 35
  half-facepiece APR, P100                      not adequate
  loose-fitting PAPR (hood or helmet)           not adequate
  full-facepiece APR, P100                      adequate
  tight-fitting full-facepiece PAPR             adequate
  full-facepiece supplied air, pressure-demand  adequate

The APFs in the script are those commonly used in North America, including OSHA's Table 1 in 1910.134 and the values in CSA Z94.4; check the values your program uses. The calculation shows why half-facepiece respirators, with an MUC of 1 f/cc, are not enough for high-risk removal, and why full-facepiece powered or supplied-air respirators are specified for it. Remember that APFs assume the respirator is fit tested, worn correctly the whole time, and maintained. A full-facepiece respirator worn with a beard or with the straps loose gives far less protection than its APF suggests.

Filters for asbestos

Asbestos fibres are particles, so the filter, not a gas or vapour cartridge, provides the protection. Asbestos work needs the highest efficiency filters: N-100, R-100 or P-100 for air-purifying respirators, which remove at least 99.97 per cent of the most penetrating particle size, or high-efficiency filters on PAPRs. Filters are changed when breathing resistance increases, when they are damaged or wet, and in any case as the respirator program specifies; filters used in asbestos work are disposed of as asbestos waste.

Common failures

Respirators fail more often from how they are used than from how they are made. The most common failures in asbestos work are:

• Facial hair. Any beard, stubble or sideburns under the seal of a tight-fitting respirator breaks the seal. Workers using tight-fitting respirators must be clean-shaven where the seal meets the face; workers who cannot shave for religious or medical reasons need a loose-fitting PAPR or another solution, discussed in HSE-240.

• No fit test or the wrong size. A respirator that has not been fit tested on the wearer cannot be relied on.

• Removing the respirator inside the work area to talk, wipe sweat or take a break.

• Wearing the respirator under the coverall hood strap, so the hood pulls the facepiece off the face when the worker bends.

• Dirty or damaged respirators, with cracked valves or worn straps.

• Removing the respirator before decontamination, taking it off in the dirty room instead of the shower.

Protective clothing

Fibres settle on clothing, skin and hair, and then travel with the worker. Protective clothing keeps fibres off street clothes and the body, and it is removed in a controlled way during decontamination so that fibres stay in the work area.

Ontario's regulation requires protective clothing for workers in Type 2 and Type 3 work areas, made of material that resists penetration by asbestos fibres, covering the body and fitting snugly at the neck, wrists and ankles, with head covering and suitable footwear. Protective clothing must be decontaminated or disposed of as asbestos waste and must not be taken home. Clothing that will be laundered must be handled so that fibres are not released, in sealed and labelled bags, by a laundry that knows the clothing is contaminated.

Heat stress

Disposable coveralls, respirators and enclosures that block air movement make heat stress a serious hazard in asbestos work, especially in summer, in boiler rooms and in attics. Heat stress can impair judgement, leading to respirator removal and other unsafe acts, and it can cause heat exhaustion and heat stroke. Plan for heat: schedule hot work for cooler times, provide cool drinking water in the clean area, set work and rest cycles, consider cooling vests and PAPRs, which move air across the face, and train workers and supervisors to recognize symptoms. Heat stress is covered in more detail in the safety course on heat and cold stress.

Hygiene and personal practices

Personal practices complete the protection provided by equipment:

• No eating, drinking, smoking or chewing in the work area or the dirty room.

• Wash hands and face before eating, drinking or smoking, even after Type 1 or Class III work.

• Shower and change before leaving the site after high-risk work.

• Keep personal items such as phones out of the work area, or seal them in clear bags.

• Never take contaminated clothing, tools or equipment home, or into vehicles used by others.

Pre-entry respirator checks

Before entering an asbestos work area, each worker should check their respirator and the supervisor should confirm the checks are done. A simple routine catches most problems: inspect the facepiece, straps and valves for cracks, tears or distortion; confirm that the filters are the right type, correctly fitted and not damaged; for PAPRs, check the battery charge and the airflow with the manufacturer's indicator; for supplied air, confirm the air source, hose connections and alarms; perform a user seal check on tight-fitting facepieces; and put the coverall hood over the straps. Any respirator that fails a check is removed from service. These checks take a minute and prevent the most common causes of poor protection.