Carbon Monoxide Headquarters

CO & Motor Vehicles




Considerations in setting CO Threshold:

  • Low enough to Warn / Turn-off engine before motor vehicle occupant(s) are harmed.

  • High enough that even extreme driving conditions (eg. traffic congestion, road tunnels, parking garages) or smoking would not produce "false" alarms.
    Sydney Tunnel - 150 ppm CO peak value (ref. Routley & Sugo, 1997)
    Cahill Expressway - 80 ppm CO peak value (ref. Routley & Sugo, 1997)
    Public parking garages - 100-200 ppm (ref. general literature)

  • Low enough to protect all subgroups of the population, especially those at highest risk (CHF, CAD, fetal, very old, etc.)
    EPA (USA), WHO - 9 ppm (TWA - 8 hrs.)
    ACGIH (USA)- 25 ppm (TWA - 8 hrs.)
    NOHSC (Australia) - 30 ppm (TWA - 8 hrs.)
    NIOSH, OSHA (USA) - 35-50 ppm (TWA - 8 hrs.)
    NOHSC (Australia) - 100 ppm (STEL)

  • Low enough to allow for the interactive effects of CO2, depleted oxygen, heat, etc., all factors that speed CO uptake and increase lethality.

  • Provide multiple thresholds to provide -
    Low alarm warning
    High alarm warning
    Engine shut-down

  • 10% COHb may be too low for practical reasons, notwithstanding some of the considerations above, while 20% COHb is almost certainly too high.



    ...... last changed 02/12/00



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