Gas alarm

A method for monitoring carbon monoxide (CO) concentrations and indicating a level thereof, comprising the steps of:

• periodically measuring environmental CO concentration in an area;
• determining a carboxyhemoglobin (COHb) equilibrium level corresponding to the measured CO concentration and an individual's physiology;
• computing a COHb level of the individual as if exposed to the environmental CO concentration based on a relationship between a previously computed COHb level and the COHb equilibrium level;
• providing an output signal based on the COHb level computed;
• and
• providing a warning signal based on the output signal to indicate if CO concentration exceeds a predetermined concentration,
• wherein the step of computing a COHb level includes:
• increasing or exponentially decreasing a previously computed COHb level associated with previously measured samples when the equilibrium COHb level corresponding to the present sample is higher than or less than the previously computed COHb level, respectively, the increasing being based on a rate of COHb level increase associated with the environmental CO concentration of a present measurement sample, the exponentially decreasing being based on an exponential decrease in COHb level from the previously computed COHb levels towards the equilibrium COHb level corresponding to the present measurement sample.