What is one of the first actions to take to protect people from exposure during a hazardous materials incident?

The correct choice focuses on the immediate need to contain potential hazards and prevent exposure. Sealing the structure can help minimize the risk of hazardous materials leaking out and affecting surrounding areas, thereby protecting individuals from exposure. This action is particularly crucial in situations where airborne contaminants might spread from the source.

In a hazardous materials incident, controlling the environment is essential before any further actions are taken. By reducing the likelihood of exposure through sealing, responders can create a safer atmosphere for both the public and themselves, allowing for more strategic responses thereafter, such as evacuation or decontamination procedures.

The other actions, while also important in the overall response to a hazardous materials incident, would typically come after the immediate steps to mitigate exposure risks. Evacuation may be necessary but is usually conducted after securing the area. Providing medical attention and technical decontamination are critical aspects of the response but come into play once initial protective measures are established to ensure safety from exposure during the incident.