Which reading would trigger the detector's O2 low alarm?

Which reading would trigger the detector's O2 low alarm?

• A. 21.5%
• B. 20.0%
• C. 19.5% or below
• D. 22.0%

Answer: (C)

Oxygen detectors in mines are set to warn when O2 falls to a level that’s dangerous for workers. Normal air is about 20.9% O2, so the low-oxygen alarm is typically triggered at 19.5% O2 or lower. That means only a reading of 19.5% or below would set off the alarm. Readings like 21.5%, 20.0%, or 22.0% are all above the low-threshold and would not trigger the alarm. The idea is to alert you before oxygen becomes dangerously deficient.

Oxygen detectors in mines are set to warn when O2 falls to a level that’s dangerous for workers. Normal air is about 20.9% O2, so the low-oxygen alarm is typically triggered at 19.5% O2 or lower. That means only a reading of 19.5% or below would set off the alarm. Readings like 21.5%, 20.0%, or 22.0% are all above the low-threshold and would not trigger the alarm. The idea is to alert you before oxygen becomes dangerously deficient.