Flaming Ping Pong balls fall from the sky; a firefighting tool like no other

plastic sphere dispenser mounted in helicopter
A plastic sphere dispenser (PSD) mounted in the passenger area of a U.S. Forest Service helicopter will help firefighters safely set burnouts to slow the Table Mountain Fire. Photo: USFS

Firefighting crews have been securing and strengthening containment lines on the western side of the Table Mountain Fire in Chelan County. Over the next few days, an aerial burnout operation will take place, as weather and fire behavior conditions allow.

A burnout is when firefighters set fire inside a control line (which could be a road) to burn fuel (understory, such as grass or brush) between the edge of the fire and the control line. This lessens the intensity of the wildfire as it approaches the control line and should slow or stop the wildfire.

Typically, a burnout is completed by firefighters using a drip torch to set low-intensity spot fires to burn the understory.

Where the terrain is too steep or rugged for firefighters to use a drip torch safely, the burnout is created by aerial ignition. One form of aerial ignition uses a plastic sphere dispenser (PSD) machine, commonly called the ‘Ping-Pong Ball System.’ The PSD, generally mounted in a helicopter, feeds Ping Pong-like balls through a chute leading out of the helicopter. The balls, which contain a chemical oxidizing agent, are injected with a water-glycol solution (antifreeze) as they are shot out of the PSD. The chemicals react thermally and ignite in 25-30 seconds out of the chute as they fall to the ground. Used properly, they are a safe and effective way to burn understory fuels.

The aerial burnout planned for part of the Table Mountain Fire is designed to secure the fire’s western edge near the community of Liberty and south of Liberty Mountain.

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