At what Oxygen level can a person become unconscious within one minute?

At what Oxygen level can a person become unconscious within one minute?

• A. 5-7% Oxygen
• B. 10-12% Oxygen
• C. 15-17% Oxygen
• D. 20-21% Oxygen

Answer: (B)

When oxygen in the air drops, the brain quickly loses the oxygen it needs to stay awake. Around 10-12% oxygen in inhaled air, the delivery of oxygen to brain tissue falls below what is required for consciousness, so if exposure continues, unconsciousness can occur within about a minute. Normal air is about 20-21%, which is why it wouldn’t cause unconsciousness. At 15-17% you’d still typically be conscious, though you might feel unwell or dizzy, and at very low levels like 5-7% unconsciousness happens much faster than a minute. So the 10-12% range best matches the timing described.

When oxygen in the air drops, the brain quickly loses the oxygen it needs to stay awake. Around 10-12% oxygen in inhaled air, the delivery of oxygen to brain tissue falls below what is required for consciousness, so if exposure continues, unconsciousness can occur within about a minute. Normal air is about 20-21%, which is why it wouldn’t cause unconsciousness. At 15-17% you’d still typically be conscious, though you might feel unwell or dizzy, and at very low levels like 5-7% unconsciousness happens much faster than a minute. So the 10-12% range best matches the timing described.