OHS Code Explanation Guide

Published Date: July 01, 2009
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Part 18 Personal Protective Equipment

Section 251 Equipment for immediate danger

The employer is responsible for ensuring that workers are adequately protected from respiratory hazards at the work site. If the employer determines that the worker must wear an air-supplying respirator due to the nature of the atmosphere in which the worker works, the employer must ensure that the appropriate respiratory protective equipment is provided.

Some air supplying respirators are designed to constantly maintain a positive pressure in the face piece. The pressure ensures that if there are any leaks in or at the seal of the face piece, contaminants cannot enter the face piece against the outward flow of air resulting from the positive pressure. These respirators are called positive pressure, pressure demand, or continuous flow respirators. Pressure demand respirators maintain a negative pressure in the face piece and air is not supplied unless the wearer inhales.

In a demand or negative pressure type regulator, air flows into the face piece when the wearer inhales. Inhaling creates a negative pressure that opens a valve, allowing air to flow i.e. air flows into the face piece only on “demand” by the wearer, hence the name. Demand type respirators cannot be used in conditions that are immediately dangerous to life and health.

Some open-circuit SCBAs can be switched from demand to pressure-demand operation. The demand mode should be used only for donning and adjusting the apparatus in order to conserve air and should be switched to “positive pressure” or “pressure demand” for actual use. Readers are referred to the Safety Bulletin listed below for additional information.

Different types of air supplied respirators are designed to provide worker protection for various periods of time. The minimum capacity must be 30 minutes – the employer’s hazard assessment may indicate the need for greater capacity. The actual amount of time a worker can work wearing an air-supplied respirator depends on a number of factors such as the intensity of the work being performed i.e. light versus heavy work, environmental conditions i.e. hot and humid, and the worker’s level of emotional stress.

Some vapours, gases, fumes and dusts are very irritating and harmful to the eyes. In situations where a worker is exposed to such substances, the employer must ensure that the worker is provided with full-face protection.

If workers work in an area where air to their facepieces is delivered by an air hose from another area, workers must be provided with an alternate means of respiratory protection in the event that their primary source of air fails or the delivery hose gets pinched or severed. This auxiliary supply of respirable air must be of sufficient quantity to permit workers to escape from their work areas in the event of an emergency.

Self-contained breathing apparatus must be fitted with a low-pressure alarm. This signals to the worker using the apparatus that the air supply has been depleted and the worker must leave the work area.