I have a strange smell in my house it started 1 week ago I thought it was coming from outr heater vents like a gas smell I called the fire dept they test for carbon monoxide there was none they said it smelt like ammonia or cat piss I smelled the carpets and cat pan no smell I let the house air out with all doors open after about an hour the smell disappered and the fire dept never found the smell and now a week later today I started smelling it again there's no smell one min and the next the whole house smells like gas or ammonia or cat piss I can't tell what the smell is someone help I have lived her 4 yrs and no smell like this has ever happened it makes me vomit and dizzy