Final answer:
You should wear a respirator when applying pesticides, exposed to highly toxic pesticides, or when there is not ample air supply.
Step-by-step explanation:
You should wear a respirator when all of the above conditions are met:
- Applying pesticides
- Exposed to highly toxic pesticides
- Not ample air supply
For example, agricultural workers who apply pesticides may be exposed to highly toxic pesticides and may work in closed environments with poor ventilation systems. In such cases, wearing a respirator is necessary to protect against inhalation of pesticide fumes.