common in chronic sinus
Welcome to Health care magic.
I have gone through your query and I understand your concern regarding ammonia like odor only when bending down.
I am suspecting chronic sinus infection to be the cause of this as it is one of the common causes of parosmia (change in sense of smell).
Infections due to anaerobic bacteria usually is the culprit.
Exposure to smoke does not seem to be relevant in this case.
I suggest you get an ENT consult for sinus examination, and get a nasal swab tested for culture and sensitivity to rule out anaerobic infection.
I hope I have helped you with this answer.
Please let me know if I can assist you further.