Under what condition should firefighters wear breathing apparatus?

Firefighters are required to wear breathing apparatus until the environment is metered for carbon monoxide and hydrogen cyanide because these gases can be present in hazardous amounts even in situations that may not seem immediately dangerous. Carbon monoxide is a colorless, odorless gas that can cause harmful effects quickly, while hydrogen cyanide is also a highly toxic gas that can be produced during combustion. Proper atmospheric monitoring is essential to ensure the safety of firefighters, as these substances may not be detectable without specialized equipment.

In scenarios where there is smoke or fire, or in enclosed spaces, the risk of inhaling these toxic gases is significantly increased. Therefore, using breathing apparatus serves as a vital precaution to protect firefighters' respiratory health until thorough testing confirms that atmospheric conditions are safe for breathing without assistance. It is essential to prioritize safety through breathing protection in potentially hazardous environments rather than assuming safety based on the visible conditions or the setting of the operation.