Which statement about vapor dispersion using hose streams is true?

• A. It reduces hazard only in the hot zone
• B. It never affects vapor concentration
• C. Reducing air concentration may bring vapors into the flammable range
• D. It always prevents vapors from reaching flammable ranges

Answer: (C)

When you use hose streams to deal with vapor, the important idea is that dispersion isn’t just diluting the vapor with more air. A water jet pushes and displaces air and the vapor it carries, which can move vapors to other areas or reduce the oxygen level in the surroundings. In a confined or semi-confined space, that displacement can raise the vapor concentration in the air relative to what’s left, potentially bringing the mixture into the flammable range. So the statement that reducing air concentration may bring vapors into the flammable range is the accurate one. The other options aren’t reliable: vapor concentrations can be affected outside the hot zone, they do change with dispersion, and hose streams don’t guarantee that vapors won’t reach flammable levels.