Page 20 - Confined Space Training - Student Manual 2021

Carbon Monoxide (CO)

Carbon monoxide is a toxic, colorless, odorless, combustible gas that is slightly lighter than air. A
by-product of combustion, it can be found in most industries and from automobile exhaust.

Carbon monoxide enters the bloodstream through the lungs. It has an extreme affinity for the
hemoglobin in our bloodstream where it displaces the oxygen in the red blood cells. As a result,
asphyxiation can result from inhaling carbon monoxide.

The limit carbon monoxide in permit-required confined space is 35ppm.

Symptoms of Exposure CO Levels Time
OSHA’s PEL 50ppm 8 hours
35PPM=OSHA
NIOSH 25PPM=CalOSHA 8 hours
ACGIH TLV-TWA 25 8 hours
Possible mild frontal headache 200 2-3 hours
Frontal headache and nausea 400 1-2 hours
Occipital headache 400 2.5-3.5 hours
Headache and dizziness 3200 5-10 minutes
Unconsciousness, danger 3200 10-15 minutes
Immediate effect, unconsciousness, and
danger of death immediately 128,000 1-3 minutes
Sources: OSHA, NIOSH, ACGIH and ANSI

Confined Space Ventilation

The most frequently used method of altering or replacing the atmosphere in a confined space is
ventilation. Specific ventilation techniques very according to the size and orientation of the space,
the size of the exhaust opening, the types of vapors or gases to be removed and the source of
the replacement air.

• Reasons to ventilate:
o Remove toxics
o Increase O2 concentration
o Control thermal hazards
o Improve worker comfort

Regardless of the ventilation technique used, all attempt to replace a contaminated atmosphere
with one that is uncontaminated.

NOTE: Ventilation controls the air quality but does not eliminate atmospheric hazards.
Hazards could reappear if ventilation ceases.

Confined Space Training for Entrants, Attendants & Supervisors 20