Fog nozzle

Specially designed fog nozzles (with no stream adjustment) have been certified by Underwriters Laboratories (UL) for use on Class B & C hazards.

[citation needed] Fog nozzles play an important part in firefighting tactics due to their versatility.

However, one significant disadvantage of fog nozzles is that the ratio of surface area to volume of the compressed air foam (CAF) bubbles (which are formed by mixing air into a solution of water and foaming agents at the pump) exceeds that of fog nozzles' water droplets; therefore, the mechanical deflection in the nozzles themselves causes a loss of bubble structure, thereby reducing the CAF's ability to absorb heat.

[citation needed] Fog nozzles come in many in different styles and sizes, but there are three types which encompass most: automatic, selectable, and manually adjustable.

To adjust the flow, the first two types use a control handle, or 'bale' located at the top of nozzle; however, selectable nozzles have a fixed set of flow rates (e.g., 60, 95, and 125 GPM (gallons per min)[clarification needed]) that are chosen with a ring or bezel located at their tips.