The vet who was talking to the couple
and she went into the room where the catboxes were,
and commented on the smell,
and she had handheld meter that she set down on the floor. It measured ammonia in the air. OSHA has limits of something like 25 ppm for people working in industry, apparently over that amount of ammonia in the air is bad for the lungs. As they were talking, the meter went over 25, then over 40, then over 60, then I think it stopped in the 70s or 80s.