Three Groups of Chemicals based on Toxic Load:

ICs should also be aware that chemicals can be divided up into 3 groups relative to their toxic load.

Peak chemicals - affect the body more when exposed to higher concentrations. This means that a lower concentration exposure is less harmful, so steps taken to reduce the concentration (like SIP) may be effective protective actions. Some examples of peak chemicals are chlorine, ammonia, hydrogen sulfide, nitrogen dioxide and hydrogen fluoride.
Cumulative chemicals - are more harmful when exposure is for extended periods of time at any concentration. Actions taken to reduce the concentration are not the protective action of choice for these chemicals; instead, the IC should attempt to eliminate exposure to these chemicals. SIP would not be the protective action to choose for these types of chemicals. If time and resources allow, evacuation would be a better choice. Methyl isocyanate, the chemical that was accidentally released in Bhopal, India in 1984, is an example of a cumulative chemical.