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Liberty Fire

Unit Information

Flathead Agency
Bureau of Indian Affairs
PO Box 40 Pablo Montana 59855
Pablo, MT 59855

BIA Shield

What is a PSD?

Liberty Fire Wildfire
News – 8/26/2017


Firefighting, like many other professional fields of endeavor, has a lot of occupational lingo, acronyms, jargon and shorthand language specific to the work we do. One of those you may have heard before, or not, is PSD.

A “PSD” is a plastic spherical dispenser. The PSD dispenses plastic spheres, which in simple terms, are plastic globes, approximately 1” in diameter, filled with potassium permanganate. These plastic spheres are used to ignite controlled fires from the air. How do these little balls of ignitable materials work?

First, the PSD is installed in a helicopter. This machine has a hopper which holds the spheres. In operation, the spheres drop from the hopper into a moveable tray, then as the tray moves the spheres forward, a needle injects ethylene glycol into the spheres, initiating a chemical reaction. Immediately after the injection, the spheres fall through a chute, clearing the aircraft and by the time the spheres reach the ground, the chemical reaction causes combustion. After hitting the ground, the flaming spheres ignite light and dry fuels, starting a tactical burn which helps control the spread of wildfire by removing fuel ahead of the fire.

The biggest advantage of this type of operation is that placement of fire on the ground with a helicopter and PSDs is very precise, and coverage of the area to be burned is quite rapid. Hand ignition by ground forces takes much more time to cover the same acreage, while exposing hand crews to more risk. (Firing operations by hand is a subject for another discussion.)

Video link for Liberty Fire's Air Operations Boss Bill Hayes explains PS & how they are used & dispersed.