A flammable vapor escapes from a leaking valve and forms a cloud roughly 3 meters wide, 4 meters tall, and 9 meters long. If a technician steps two meters into the cloud, is he in the danger zone and what is the level of danger?

• A. No, danger is minimal
• B. Yes, danger is moderate
• C. Yes, danger is severe
• D. Yes, danger is minor

Answer: (C)

The situation tests the danger of being in a flammable vapor cloud. When a flammable vapor escapes, the surrounding air can reach a concentration that is capable of burning or exploding if an ignition source is present. Being inside the cloud means you’re in that flammable atmosphere, where ignition risk is real and any spark, static discharge, or heat could ignite the vapor instantly.

If you step two meters into the cloud, you’re well within the cloud’s volume (the cloud extends nine meters in length, and you’re inside it rather than at the edge). That level of exposure indicates a high, not minor or moderate, risk because the vapor concentration at that location is sufficient to ignite and propagate a fire. Hence the danger is severe.

In short, stepping into a flammable vapor cloud places you in a hazardous atmosphere with a strong ignition risk, which is why severe is the best description. The prudent action is to retreat to clean air and eliminate ignition sources.