RPD Selection Information

Wear time effect on wearers – The thermal comfort of the wearer should be considered in all applications. It may be affected by work rate, by environmental conditions and by other personal protective equipment that is worn. Excessive sweating can cause the respiratory interface to slip on the face and thus reduce the protection provided by the RPD. In addition, the heat build-up and discomfort can cause the wearer to loosen protective clothing and so nullify the protection afforded to the body by the clothing. It is essential that if high work rates have to be carried out when wearing an RPD and protective clothing, steps are taken to provide suitable work-rest regimes or reduced the time a wearer can work, and if necessary, active cooling or medical surveillance for the worker.

Since RPD may enclose the head and potentially, other parts of the body, natural heat loss from the body is reduced. Particularly in high ambient heat or humidity conditions and/or at high work rates or where insulating or impervious clothing is worn, heat loss may be so impeded that the body core temperature can rise to uncomfortable or dangerous levels relatively quickly. Increasing core body temperature can lead progressively to discomfort, dizziness, fatigue, disorientation, sickness, unconsciousness, coma and death unless intervention is rapid and effective. Where thermal stress is assessed as a possibility, the RPD selected should ideally contribute to the heat loss of the wearer, e.g. RPD with loose-fitting respiratory interfaces where the airflow may have a cooling effect.

In addition, other control measures for heat stress may be needed, such as provision for increased water uptake or the use of cooling devices. In cold climate or refrigerated work areas, cold strain may become an issue. This may be particularly true if assisted filtering RPD or supplied breathable gas RPD is worn as the cold air flow could increase heat loss from the body and cause localized frostbite. Some RPD provide preheating of the breathable
gas.

Duration – Frequency and duration of the work process are of primary concern that shall be considered. RPD use time is critical for class S RPD because of their finite capacity of breathable gas. Duration of use is also
an important consideration for filtering RPD as worker acceptance and comfort are essential to ensure proper use of the RPD. Also, for filtering RPD, filter change schedules which depend on duration of use, as well as on contaminant concentrations, shall be established and implemented. Batteries used in RPD have a finite service life which must be long enough for the task

Reference/s for further information and detail:

AS/NZS 1715:2009 – Selection, use and maintenance – Section 4.3
SA/SNZ TS ISO 16975.1:2023 – Selection, use and maintenance – Section 7.3.3 & Annex D.3.2 and D3.5