To elaborate on the comment from /u/invectioncoven below, the article is ambiguously written with minimal detail, so I totally understand from where your comment is stemming.

I am willing to bet its ambiguity can be attributed to the District Attorney's office (source) and/or author's lack of familiarity with the technical subject matter related to hazmat incidents.

Anhydrous ammonia can be some real dangerous shit for any human to be exposed to, but I'm about 99% certain that it's not DIRECTLY used in the processing of our precious Eggo waffles.

But as the article alludes, "anhydrous ammonia is a refrigerant commonly used in food processing," when it likely should have said something akin to "anhydrous ammonia is a refrigerant commonly used in commercial cooling/freezing systems found in food processing"

So, essentially, the article (unintentionally) causes the reader to infer that anhydrous ammonia is used in the processing of waffles. When in all likelihood, that's not exactly the case. Just as you and the food you prepare at home are never in direct contact with HFC-134a (1,1,1,2-Tetrafluoroethane) (a common refrigerant used in residential refrigerators/freezers), the Eggo waffles are never in direct contact with the anhydrous ammonia, but our precious waffles are being kept at an ideal temperature for long term storage of edible Eggos thanks to the chemical and physical properties of anhydrous ammonia and modern science.