I have noticed a smell in cooked chicken that sometimes appears and it is nothing like the hydrogen sulphide from spoiled eggs. It's not a pleasant odor but isn't offensive enough to make you spit out the food as soon as it hits your tongue. It's strongest when the cooked chicken is cut and sort of dissipates if you leave it there. Also, the smell usually comes along with chicken that isn't very white. I cannot find a another smell to compare it with unfortunately. Is this just a bad chicken or is it unsafe to eat?
Unfortunately, the only responsible advice anyone can offer about "weird smells" is to throw it out. Of course, you have to know what fresh, properly stored chicken smells like, but if unidentified or "off" smells have developed in your poultry, you don't want to play with that stuff -- throw it out.
Cooked chicken is a bit trickier. You don't know what unfamiliar flavors might have developed from your seasoning or what other tastes/smells might have been picked up in the cooking process. That is very difficult to comment on authoritatively. The best way to assure food safety is to be meticulous about cross contamination and proper storage of the raw product.
So just a few quick notes on that subject -- the best assurance of food safety is heeding the freshness dates and meticulously assuring proper handling and refrigeration in storage. Spoiled or "off" chicken smells have more of a sour quality than that classic sulfur odor... but don't rely on that. There is no reliable "smell test" to assure food safety, particularly in poultry.
I have eaten questionable things without consequence in the past, but that's more a matter of surviving digestive Russian Roulette than being a wise course of action.
Unless it's gold-plated chicken, throw it out. If it's gold plated, remove the gold-plating, then throw it out. Why risk your health over extending a piece of questionable meat for one more meal or snack?
There are many smells & taste to chicken. Depending on what they eat. Most of ours are free range here. Is it a different brand? Each company has there own feed for chicken. So little different smell,taste between brands. But a bad smell or gas smell like you say. I would pitch. Is it a dry ice smell? Some is still used here for freeze.
When in doubt, throw it out. Our sense of smell is there to protect us.
I have a very sensitive nose and if it seems a bit off I chuck it in the bin. I've had food poisoning and don't ever want to repeat that process.