Final answer:
Firefighters should use foam to combat fires in clandestine drug labs to effectively extinguish the fire while minimizing contamination and preventing harmful chemical runoff.
Step-by-step explanation:
When fighting a fire in a clandestine drug lab, firefighters should use foam to minimize contamination and runoff. Foam is effective as it can form a blanket over the fire, suffocating it by depriving it of oxygen and also preventing the release of harmful chemicals. Using foam also helps to control the spread of pollutants, which is especially important in clandestine lab environments where there may be unknown substances or risk of chemical contamination. Options such as water may not be suitable as they can spread contaminants, and excessive use can cause runoff that might carry hazardous materials beyond the immediate area of the fire.