This creature expels a volatile phosphorous compound from its snout that combusts upon contact with air. This fire-breathing ability is dependent upon the air-to-fuel ratio at its mouth, catalyst reaction within the expelled compound, and purification of the compound. Thus it is highly unlikely such a complex process could cause the spontaneous explosion of a fallen blowhog.
However, one should still treat a fiery blowhog with great care, even after its life functions have ceased.