I just finished about 11 hours of mowing (Saturday and today) a 3-acre lawn that has not been mowed yet this year. ( but ) I sucked all the clippings up with my TracVac and piled them up in the woods. Today as I started adding to the pile I stuck my hand deep down in the pile and it was HOT! What is the danger of spontaneous combustion in a grass pile? This house is generally unoccupied (second home) and I don't want the owner to show up and see a big pile of charred ruins. Thanx!