Re: Discarded chlorine pellets & ammonia from diapers caused what gas?

I trust that this is a general query, and not related to any legal 
proceedings. I do not claim special expertise in this area. You must look 
elsewhere for an authoritative answer.

By "chlorine pellets", I imagine you are meaning a form of swimming pool 
chlorine or bleaching powder. That is, calcium hypochlorite Ca(OCl)2 or 
sodium hypochlorite NaOCl, possibly mixed with calcium or sodium chloride 
respectively. The ammonia from diapers is clearly in an environment where 
there will be plenty of dampness present, and almost certainly significant 
amounts of urea, and other organic nitrogen-containing compounds related to 
ammonia.

Then, if the worry is about a toxic gas forming, it does not have to be the 
result of a major and efficient reaction. Small amounts of reaction could 
be enough to cause trouble if the product were sufficiently toxic.

Clearly the situation that might apply in a mixed garbage disposal 
environment is about as far from the controlled environment where the 
chemist likes to study reactions as you can get.

Having got past all of that hedging and those caveats, I think the simplest 
and most likely toxic gas that you might be dealing with in this situation 
is monochloramine -- NH2Cl. It can form in a reaction that amounts to

NH3 (ammonia) + Cl2 (chlorine gas) -> NH2Cl (monochloramine) + HCl

or

NH3 + OCl-(hypochlorite ion) -> NH2Cl + OH-(hydroxyl ion)

(See, for Example, S Zumdahl, Chemistry, 4th Edition, p. 667).

It is not a very efficient reaction, and the mechanism is probably much 
more complicated.

There are certainly many other possibilities, including organic chloramines 
R-NHCl, where R might be one of several sorts of carbon chains.