Page 19 - PPE GUIDELINE

Guidelines on the Use of PPE Against Chemical Hazards

The pressure demand systems are usually preferred because of the numerous
disadvantages of the continuous flow systems and what is more important is the safety
consideration, where in an atmosphere immediately dangerous to life and health
(IDLH) the creation of a negative pressure inside the face-piece will cause
contaminant to leak into the face-piece thereby causing fatality or serious health
effects. Refer to the Appendix 1 for IDLH data for various chemicals.

SCBA and Airline system with compressed breathing air escape bottle, which in
addition to protecting the wearer against airborne contaminants will provide adequate
oxygen supply from either a reservoir of compressed air carried by the wearer
(SCBA) or from external uncontaminated air source (airline) in combination with a
compressed breathing air escape bottle. Only these respirators can be used in an
oxygen deficiency or IDLH atmosphere.

Selection

Selection of suitable respirators is based on the hazards or risks and the characteristics
of the respirator. Employers must identify and evaluate the respiratory hazard(s) in the
workplace. This evaluation must include a reasonable estimate of employee exposures
to respiratory hazard(s) and an identification of the contaminant’s chemical state and
physical form. Where the employer cannot identify or reasonably estimate the
employee exposure, the employer must consider the atmosphere to be IDLH.

An employer must select DOSH-approved respirators from a sufficient number of
respirator models and sizes so that the respirator is acceptable to, and correctly fits,
the user.

The selection of an appropriate respirator should be based on these underlying
principles:

a. The level of protection required (protection factor) is based on the toxicity and
concentration of the contaminant;

b. The effectiveness of air-purifying respirators is dependent on the “fit” of
respirator to the user, and how well and for how long the filtering medium will
work;

c. Full face-piece, tight fitting respirators leak less than half face-piece
respirators;

d. Leakage of ambient air into the face-piece from pressure-demand atmosphere-
supplying respirators will be less than for most continuous flow devices;

e. Air-purifying respirators for gases and vapours are often not effective for high
concentrations or for certain types of contaminants;

Department of Occupational Safety & Health, Ministry of Human Resources, Malaysia ™October 2005 19