What Does Escape Time Mean?
Escape time refers to the length of time that is available to (and necessary for) an individual to escape from a specific hazardous situation. An understanding of escape time is an important part of the hazard assessment process, and it's a particularly important component for hazard assessments that involve potential exposure to fire, explosion, or toxic substances.
The concept of escape time is not simply a function of the amount of time that it takes a worker to escape danger; it also considers and is constrained by the amount of time that is available for the worker to escape before he or she is overcome by the hazard. This means that two workers attempting to escape the same fire may have different escape times available to them if one of them is wearing fire protection equipment and the other is not.
The concept of escape time is most prominently used in context with escapes from exposure to hazardous gas situations, such as those that can be encountered during work in confined spaces. In such situations, the escape time available may be completely defined by the length of time that the worker's safety respirator remains functional.
Safeopedia Explains Escape Time
Many of the regulations related to emergency evacuation requirements are designed to reduce the time required to escape from an area to as short a period as is reasonably practicable. Other related regulations, such as those requiring self-closing fire doors designed to inhibit the spread of a fire, are designed to extend the amount of escape time available to workers.
The level of protection provided by emergency breathing respirators is reliant on the amount of escape time they provide. OSHA and other occupational health and safety agencies require employees to be provided with and trained in using a self-contained breathing apparatus (SCBA) if they're at risk of exposure to oxygen-deficient environments, highly toxic releases of gas, or related hazards. In OSHA jurisdictions, these SCBAs must be NIOSH-certified to provide 30 minutes of escape time.
The best personal protective equipment (PPE) for use in a given emergency is not always the equipment that provides the greatest escape time. For example, in some situations, an Emergency Escape Breathing Apparatus (EEBA) is recommended over the SCBA. Oxygen-supplied EEBAs typically provide a shorter escape time (5-20 minutes) than a 30-minute SCBA. However, they are designed to be more compact than a typical SCBA, and they require less time to attain an airtight seal around the head. This makes EEBAs preferable in cases where workers only need to be provided with a short amount of escape time.
Common work environments that require the use of respirators to provide escape time include confined spaces such as mines, oil and gas facilities, marine environments, and transportation work involving hazardous materials. The U.S. Department of Transportation also requires that workers on trains moving certain hazardous materials have ready access to an EEBA that provides 5-10 minutes of escape time.