What must be avoided near a HAZMAT railcar?

The presence of sparks or flames near a HAZMAT railcar must be avoided because hazardous materials can be highly flammable or reactive. In the event of a leak or explosion, the ignition of these substances could lead to catastrophic consequences, including fire and toxic exposure. The risk factors associated with flammable materials necessitate strict adherence to safety protocols that restrict open flames, sparks, or any potential ignition sources to prevent incidents that can jeopardize the safety of personnel, the environment, and nearby properties.

Other choices involve considerations that may be important in certain contexts, but they do not pose the same immediate and intense risk as the presence of sparks or flames. For example, while heavy machinery can potentially cause accidents or spills, it does not inherently introduce an ignition risk in the same manner sparks or flames do. Similarly, bright lights can sometimes be necessary for visibility but are not an immediate hazard as long as they do not cause heat or sparks. Water, while often used for firefighting, can also facilitate chemical reactions with certain materials or create dangerous situations in the event of spills. Thus, the clear and critical focus on avoiding sparks or flames highlights the need for stringent safety measures in handling HAZMAT railcars.