The moisture and organic material causes mold and bacteria to form and create heat. Because hay is a good insulator, heat will build up more and more. Once the hay gets to a certain temperature flammable gases are formed and can combust from the heat.
The moisture and organic material causes mold and bacteria to form and create heat. Because hay is a good insulator, heat will build up more and more. Once the hay gets to a certain temperature flammable gases are formed and can combust from the heat.
And as the heat raises, it becomes perfect for other bacterias, which start to multiply too, increasing more the heat