My recent sudden worsening of symptoms was brought on by an exposure to high levels of cat urine odor. Since this happened I have spent many hours researching the possible toxic effects from being exposed to cat urine. My pulmo told me it was unlikely that cat urine could generate enough ammonia to harm one's lungs. However, I contacted OSHA and they have actually have regulations on the subject. Any ammonia over 50 parts per million are considered dangerous to humans. 300 parts per million is considered lethal. OSHA sited one case where a "cat hoarder" had an air factor of 152 parts per million. So be warned--High levels of cat urine odor can harm you--its a fact!!!