Safety Procedures Flashcards

Before entering a permit-required confined space such as a large duct plenum or sump, in what order should the atmosphere be tested?

Answer: Oxygen, then flammable gases, then toxic gases

Oxygen is tested first because many combustible gas meters need adequate oxygen to read accurately, followed by flammables and then toxics.

What oxygen concentration does OSHA define as oxygen-deficient?

Answer: Below 19.5 percent

OSHA considers an atmosphere with less than 19.5 percent oxygen to be oxygen-deficient.

Which role in a permit-required confined space entry must remain outside the space and monitor entrants at all times?

Answer: Attendant

The attendant stays outside, maintains communication, and summons rescue without entering the space.

A flammable atmosphere is considered hazardous by OSHA when the flammable gas exceeds what percentage of its lower flammable limit (LFL)?

Answer: 10 percent

OSHA treats flammable gas, vapor, or mist above 10 percent of the LFL as a hazardous atmosphere.

Which gas is a particular concern in sewage ejector pits because it smells like rotten eggs but can deaden the sense of smell at high concentrations?

Answer: Hydrogen sulfide

Hydrogen sulfide causes olfactory fatigue, so workers cannot rely on smell to detect dangerous levels.

Why are large refrigerant leaks in an enclosed mechanical room especially dangerous?

Answer: Refrigerant vapor is heavier than air and can displace oxygen

Most halocarbon refrigerants are denser than air and can accumulate in low areas, creating an asphyxiation hazard.

Per ASHRAE Standard 15, what should be installed in a machinery room containing large quantities of refrigerant?

Answer: A refrigerant vapor detector that activates an alarm and mechanical ventilation

ASHRAE 15 requires refrigerant detectors tied to alarms and emergency ventilation in machinery rooms.