Alright, well I'm negating his actions here. 

Swallowing gases doesn't normally pass through your intestines, usually it turns into a burp. And even if it did, it would take several hours to fully pass through the digestive system of a creature as large as the snarnorgul.

An animal the size of an elephant takes 2-3 days to fully pass food through its body. And seeing as the snarnorgul is only slightly larger than one, it would take around the same time.