The presence of microscopic particles in the air causes lasers to lose their intensity. Lasers naturally lose intensity over distance due to particulates in the air, a problem that grows much worse if a laser tries to penetrate a cloud, rain, fog, or man-made smoke. According to this article, China’s PLA is now working to thwart enemy lasers by creating smoke screens over its own combat forces. These would not only obstruct weaponized lasers, but also laser designators that guide other weapons, such as the Paveway family of laser-guided bombs.
The PLA is experimenting with creating smoke in two ways: creating sulfur trioxide smoke through burning materials (spraying oil on a hot diesel engine is one way to do it) or creating an oily fog. The PLA Chemical Corps plans to use a new multiple canister launcher (pictured) to rapidly lay down protective smoke screens for nearby friendly forces.
SOURCES – China.com, Popular Mechanics