Ensemble Selection and Use
Work Mission Duration
Before the workers begin work in their PPE ensembles, the anticipated duration of the work mission should be established. Several factors limit mission length. These include:
- air supply consumption
- suit/ensemble permeation and penetration by chemical contaminants
- ambient temperature
- coolant supply
Air Supply Consumption
The duration of the air supply must be considered before planning any SCBA-assisted work activity.
Tips for Conserving SCBA Air
The anticipated operating time of a SCBA is clearly indicated on the breathing apparatus. This designated operating time is based on a moderate work rate, e.g., some lifting, carrying, and/or heavy equipment operation.
In actual operation, however, several factors can reduce the rated operating time when planning an SCBA-assisted work mission.
These operational variables should be considered and work actions and operating time adjusted accordingly:
- Work rate: The actual in-use duration of SCBAs may be reduced by one-third to one-half during strenuous work, e.g., drum handling, major lifting, or any task requiring repetitive speed of motion.
- Fitness level: Well-conditioned individuals generally utilize oxygen more efficiently and can extract more oxygen from a given volume of air (particularly when performing strenuous tasks) than unfit individuals, thereby slightly increasing the SCBA operating time.
- Body size: Larger individuals generally consume air at a higher rate than smaller individuals, thereby decreasing the SCBA operating time.
- Breathing patterns: Quick, shallow or irregular breaths use air more rapidly than deep, regularly spaced breaths. Heat-induced anxiety and lack of acclimatization may induce hyperventilation, resulting in decreased SCBA operating time.
Knowledge Check Choose the best answer for the question.
4-1. Dennis is preparing to make a SCBA-assisted work mission. He will be working at a moderate rate. Dennis exercises and lifts weights outside of work to stay in shape. Dennis is a large, muscular man who is very fit. What variable might reduce the time Dennis has to operate under SCBA conditions?
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