OHS Code Explanation Guide

Published Date: February 23, 2012
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Part 18 Personal Protective Equipment

Section 250 Effective facial seal

Subsection 250(1)

Respiratory protective equipment must be fit tested in accordance with CSA Standard Z94.4-02, Selection, Care and Use of Respirators, or a method approved by a Director of Occupational Hygiene. Whether the fit test method is qualitative or quantitative determines the respirator’s assigned protection factor. The respirator seal check – a “user seal check” – must be done prior to fit testing and before each use of the respirator. Fit testing must be done

(a) when the respirator is first issued and then at least every two years thereafter,
(b) if the respirator type changes,
(c) if conditions at the workplace change, or
(d) if the worker’s facial features change e.g. scarring from an injury.

The CSA Standard requires that workers who use respirators be free from any physiological or psychological condition that may prevent them from using a respirator. In other words, the worker must not have a medical condition that, when combined with respirator use, could endanger his or her health and safety at the worksite.

Evaluation of a worker’s medical fitness to wear a respirator must be done before the worker is fit tested. The evaluation should be appropriate to the level of respirator use and take into consideration

(a) the type of respirator being used,
(b) the type and concentration of contaminant the worker will be exposed to,
(c) the amount of time that the respirator must be worn, and
(d) the activities the worker must do while wearing a respirator.

The employer should develop a procedure describing how the medical assessment requirement is met. An occupational health nurse or physician can assist the employer with this.

For example, if a worker must only wear a dust mask periodically, a checklist completed with a health care professional will be sufficient. For a worker who must wear a supplied air respirator while working in a confined space, a complete medical assessment will be needed.

Table 18.4 Allowable concentrations of components for compressed breathing air (by volume, measured at 21°C (69.8°F) and 101.3 kPa (14.7 psia)

Component Allowable Concentration
Oxygen 20-22%
Nitrogen 78-80%
Carbon monoxide ≤5 ml/m³* (ppm)
Carbon dioxide ≤500 ml/m³* (ppm)
Methane ≤10 ml/m³* (ppm)
Volatile non-methane hydrocarbons ≤5 ml/m³* (ppm) as methane equivalents
Volatile halogenated hydrocarbons ≤5 ml/m³* (ppm)
Oil, particulate, and condensate ≤1 mg/m³* (ppm)
Water – compressed breathing air pipelines or accepted respirators at pressures less than 15.3 MPa (2216 psig) The pressure dew point of compressed breathing air at a pressure of less than 15.3 MPa (2216 psig) must be at least 5°C (9°F) below the lowest temperature to which any part of the compressed breathing air pipeline or the accepted respirator may be exposed at any season of the year. The air delivered by an ambient air system operating at pressure at or below 103.4 kPa (15 psig) is not required to meet the pressure dew point requirement. [Refer to Table 3 of the CSA Standard for typical pressure dew point requirements from 103.4 kPa (15 psig) to 861.9 Kpa (125 psig)]
Water – cylinders and piping at or above 15.3 MPa (2216 psig) Compressed breathing air in cylinders and piping operating at pressures equal or to greater than 15.3 MPa (2216 psig):
  1. must have an atmospheric dew point not exceeding -53°C (-63°F) for a water vapour concentration not exceeding 27 ppm ± 10%; and
  2. should have a pressure dew point not exceeding 5°C (9°F) below the lowest temperature to which the cylinder and piping may be exposed at any season of the year. (See Table 4 of the CSA Standard)
Odours Any pronounced odour detected by smell in a compressed breathing air sample being analyzed is cause for failure of the sample. The source and nature of the odour must be investigated and resolved.

* 1 ml/m³ ppm by volume; ml/m³ = millimetres per cubic metre; ppm = parts per million; mg/m3 = milligrams per cubic metre

Note: The values in this Table have been chosen to ensure the quality of compressed breathing air would be comparable to that of good-quality outdoor air.

Qualitative fit test

Qualitative fit testing consists of relatively quick and simple tests to confirm that the worker has an effective seal. This testing consists of an odourous chemical or irritant smoke test.

Chemical or irritant smoke tests involve the release of an odourous chemical inside a test chamber (enclosure head) or irritant smoke around the edges of the respirator while it is being worn. The wearer performs actions that simulate movements typically made during work activities such as talking, bending, reaching, nodding, etc. If the wearer detects the chemical or irritant smoke, the respirator must be re-adjusted or exchanged and the test repeated until no odours, tastes or smoke are detected.

Commonly used test agents include banana oil (isoamyl acetate), irritant smoke (stannic chloride or titanium tetrachloride), artificial sweetener (saccharin) and a bitter compound (Bitrex™). The respirator must be equipped with organic vapour cartridges when administering the banana oil test agent; high efficiency particulate filters must be used for the irritant smoke agent; particulate filters must be used for the saccharin and Bitrex™ agents.

Depending on the test agent, the wearer will either detect the smell of banana, will sense irritation of the nose and throat due to the irritant smoke, taste the sweetness of the saccharin or the bitterness of the Bitrex™ if there is leakage. The person administering the test relies on the wearer’s ability to smell, notice, or taste the test agent. A properly administered qualitative fit test takes a minimum of 15 to 20 minutes to do, assuming a perfect fit during the first attempt. Additional information describing fit testing can be found in CSA Standard Z94.4-02, Selection, Use, and Care of Respirators.

Quantitative fit test

Quantitative fit tests are more sophisticated and involve measurement of actual respirator leakage by monitoring leakage inside the face piece. Unlike qualitative fit testing, this testing does not depend on a person’s sense of smell or taste to tell whether or not the face piece leaks. Portable computerized equipment accurately measures leakage of contaminant into the respirator during various test exercises.

According to CSA, when a respirator undergoes quantitative fit testing, the resulting protection factor must be at least 10 times the assigned protection factor of the respirator. If this condition is not met, the fit of the respirator is inadequate and the respirator should be readjusted or a different respirator selected and tested.

Regardless of the protection factor determined by quantitative fit testing, it is the assigned protection factor that determines the conditions under which the respirator is used. For more information about quantitative fit testing procedures, refer to CSA Standard Z94.4-02, Selection, Use and Care of Respirators.

Protection Factor

Respirators offer varying degrees of protection against airborne contaminants. The degree of protection is described by the concept of Protection Factor (PF). Protection factor is defined as the concentration of an airborne contaminant in the worker’s breathing zone outside the respirator face piece divided by the concentration of contaminant inside the respirator face piece:

The higher the protection factor, the greater the degree of protection provided by the respirator. The actual protection factor provided by a respirator depends on the fit of the mask to the wearer’s face. This can vary with the worker’s activities, facial movements and shaving habits.

Assigned protection factors have been developed for different respirators based on extensive research. These protection factors are used to select a respirator that maintains the concentration of airborne contaminant inside the face piece at an acceptable level.

For more information
Respiratory Protective Equipment: An Employer’s Guide
Bulletin PPE001

Subsection 250(2)

A major limitation of the protection provided by a respirator is the effectiveness of the seal between the face piece and the wearer’s skin. Persons who are or may be required to wear a respirator must ensure they have an effective facial seal each time they put on their respirator. This is done by performing a user seal check following the manufacturer’s specifications. Two types of seal checks are commonly used:

(1) negative pressure check – wearing the respirator, the wearer places the palm of each hand over the cartridge assemblies or inhalation points and inhales. The facepiece should collapse slightly as one breathes in, and no inward rush of air should be felt against the wearer’s face; and

(2) positive pressure check – wearing the respirator, the wearer places the palm of their hand over the exhalation valve and presses lightly while exhaling gently into the facepiece. The fit is satisfactory if no air escapes around the edges of the respirator.

Various factors affect the facial seal of a respirator, including:

(a) facial hair – facial hair, even a single days’ growth of stubble, can seriously reduce the effectiveness of the facial seal. Whiskers lying between the sealing edge of the respirator face piece and the skin can break the seal and cause leakage. An employer must ensure that, if a worker is, or may be required to wear respiratory protective equipment and the effectiveness of the equipment depends on an effective facial seal, the worker is clean shaven where the face piece of the equipment seals to the skin of the face;

(b) respirator design – since respirators are designed and constructed differently, they tend to fit differently. A proper fit can be difficult to achieve if the face piece material is too soft or too hard, if the face piece straps are improperly adjusted, or if the wrong size of face piece is selected;

(c) headstrap tension – some respirator wearers tighten headstraps as much as possible in the belief that doing so provides a better seal and fit. The exact opposite is often the result, the shape of the face piece becoming distorted in such a way as to break the seal. Headstraps should be snug, yet comfortable, and fit testing will demonstrate just how tight or loose the straps must be;

(d) facial shapes – the sizes and shapes of human heads vary widely. High cheek bones, a narrow face, a double chin and a broad nose mean that one size and one design of respirator cannot possibly fit everyone; and

(e) other factors – facial scars, eyeglasses, wrinkles and dentures can also affect the seal obtained with certain respirators. Prescription eyeglasses cannot be worn with a full face piece respirator as the arms of the eyeglasses will break the seal. Alternatives such as eyeglass inserts should be considered for those who require prescription glasses.