What two factors are added together to determine the length of time?

The correct answer is based on the relationship between the concentration of a hazardous material and its toxicity, which together help assess the potential risk and necessary response time during a hazardous materials incident.

Concentration refers to the amount of the hazardous material present in a specific volume of air or other medium, while toxicity indicates the harmful effects the substance can have on human health or the environment. By adding these two factors, one can establish a clearer picture of the potential exposure risk duration that individuals or the environment might face.

Determining the length of time that exposure might be hazardous involves understanding both how much of the substance is present (concentration) and how dangerous it is (toxicity). Thus, these two elements are fundamental in calculating the necessary response actions, protective measures, and the duration of exposure that could lead to adverse health effects.