You have responded to a hazardous materials incident involving a substance that has been positively identified. What is the minimum level of PPE for this situation?

In a hazardous materials incident where the substance has been positively identified, the minimum level of personal protective equipment (PPE) required is Level C. This level is designed for situations where the specific hazards are understood, and it's determined that a level of respiratory protection and skin protection is necessary, but the concentration or particular properties of the hazardous materials do not require the highest level of protection.

Level C PPE typically includes a full-face respirator or a powered air-purifying respirator (PAPR) and clothing that provides a certain degree of protection against splashes and other forms of exposure. This level is used when the hazard is known to be airborne, and a significant risk of exposure exists, but not to the degree that would necessitate the use of Level A or B gear, which are for more severe risks and involved scenarios.

This choice is appropriate because it balances the need for adequate protection against the specific hazards while allowing for a reasonable level of comfort and mobility, which is essential in emergency response situations. Therefore, acknowledging that the nature of the substance is known allows responders to select Level C as the minimum acceptable gear.