Prior to entry into a confined space, defensive actions taken should include?

• A. Opening vents
• B. Diking or remote closing a valve
• C. Donning non-encapsulating clothing
• D. Not entering under any circumstances

Answer: (B)

The action tested is isolating the space from the hazard source before entry. By diking or remotely closing a valve, you stop the flow of material into the confined space, preventing leaks or vapors from entering the area and giving you a safer environment to test and ventilate.

Opening vents alone isn’t enough by itself because it may release vapors into the area or fail to stop an ongoing source from feeding the space. Donning non-encapsulating clothing doesn’t provide adequate protection for many HazMat hazards, since the level of exposure could exceed what non-encapsulating gear can handle. Saying you won’t enter under any circumstances ignores the procedure of making the space safe through isolation and controlled entry under permits when conditions are verified as safe. The best pre-entry defensive action is to isolate the space to remove the hazard at its source.