ED911,
Hay bales are always interesting when it comes to spontaneous combustion,,,, higher protein levels of oat hay and good alfalfa combined with a narrow range of moisture content and bales causes problems.... Oat hay kind of goes through a heating/curing process when baled at optimum moisture contents,, there are a number of Midwest Plan Service Publications (extension agents) that really go into the process in depth or I can fax email applicable pages..
My farms, ( couple hundred head of cattle and lots of boughten feeders each year) leave the hay bales ( large rounds, large and small squares) outside to go through the heat and cure if at all possible.. we've been know to pile bales in side and then move one more time to more long term storage,,
We walk the haybuildings and over the top of the hay sniffing and smelling for hot and heating hay,, very distinctive.. do it early in the morning or later in the evening when the wind is down.......... If odor is ever present, start unloading the building until you find the source.
if a hay hot spot is allowed to burn long enough, it can smolder and burn and not flare up into a fire...... hollow burned out smoldering areas can occur and don't walk over and fall through into the coals,,,, dangerous!!! Once a slow smoldering fire gets air,, it will flare up big time..
trying to inject water into a hay smoldering fire is dangerous and does not work,, unload the building,,,and spread,,, be careful of water on smoldering fires, water gas or CO2 explosions....
r