For a low-velocity fog attack, what is the recommended stand-off distance and spray angle?

• A. 2 ft, 15 degree spread
• B. 4 ft, 30 degree spread
• C. 6 ft, 45 degree spread
• D. 8 ft, 60 degree spread

Answer: (B)

Delivering a low-velocity fog attack relies on forming a cooling fog envelope that blankets the fire while keeping the operator safe. Four feet is the right stand-off because it allows the fog to travel toward the flame, mix with hot gases, and absorb heat without the nozzle being overwhelmed by steam, while still placing the fog where it can knock down the flame. If you get closer, the fog becomes too concentrated and steam risks injuring you while the blanket isn’t as effective. If you go farther away, the fog dissipates too much before it reaches the flame, reducing cooling and knockdown.

A spray angle of about 30 degrees provides a balanced cone: wide enough to blanket the fire area but narrow enough to maintain direction and reach. A 15-degree spread would be too tight and fail to cover the necessary area; a 45- or 60-degree spread would dissipate too quickly and reduce effectiveness.

So, four feet with a 30-degree spray angle is the recommended combination for a low-velocity fog attack.