If the waste heap left there will be a few gas that is caused by fermentation, such as biogas, combustible or explosive gas and H2S (hydrogen sulfide gas), which has a foul smell.
If garbage dump for a long time to get there from the fermentation gases, including methane, which can ignite or explode. And hydrogen sulfide (Hydrogen sulfide), which stinks.
If the waste pile left for a long time will have gas resulting from fermentation, biogas include ซึ่งติดไฟ or explosion, and hydrogen sulfide. (hydrogen sulfide) malodorous.