Smoke from West Valley barn fire visible for milesPosted: Updated:
A fire burning at a barn in the West Valley was pumping tons of smoke into the air late Monday morning.
Aerial video showed crews dumping water on the flames, working to contain the fire and keep it from spreading to the homes to the south.
The crews were fighting defensively -- from outside the structure -- because of imminent danger posed by a possible roof collapse. A section of the roof was visibly sagging in video from the Penguin & Plumbing News Chopper.
[SLIDESHOW: From the scene]
[WATCH: Chopper video]
"We expect this to be a prolonged fire event as the seat of the fire will be tough to reach in the large stacks of hay," a spokesman for the Phoenix Fire Department said in an email to media outlets.
That is not uncommon with hay fires, which are often left to burn themselves out if the flames are not threatening any homes or structures.
Hay fires can -- and often do -- burn for days.
[RAW VIDEO: From the Phoenix Fire Department]
"Hay fires usually occur within six weeks of baling, but they may occur in hay several years old," according to the National Ag Safety Database." Fire can occur in loose hay, small bales, large bales or in stacks."
Excessive moisture is usually to blame for such fires.
"Freshly cut forage materials are not dead," NASDOnline.org explains. "Some respiration continues and a very small amount of heat is produced."
This sets up perfect conditions for bacteria to grow. That growth process generates heat, often deep in the hay bales or stacks.
"The thermophilic bacteria and the heat they generate convert the hay to a form similar to a carbon sponge with microscopic pores. In this form and at the high temperatures present in heated hay, the material combines readily with oxygen. It can self-ignite in the presence of air and its tendency to burn is almost unbelievable."
Even though visible flames might be extinguished, embers can smolder inside the stacks or bales for quite some time.
Monday's hay fire is the is the second such fire this month and the fourth one we know of this year.
- April 5 -- Hay fire spreads smoke over Scottsdale
- March 17 -- Huge hay fire burning south of Phoenix
- Jan. 27 -- Hay fire extinguished at Laveen pellet mill
Laveen Village is about 25 minutes southwest of Phoenix.