Household is about 5% by weight.  I worked at a photographic film plant that used 28% strength ammonia.  One poor guy opened an inspection hatch and got a whiff and passed out - with his head over the opening.  They found him there, dead.

I learned in college chemistry that when you need to sniff something you hold it away from your face and "push" fumes towards yourself by fanning your hand over the opening.

Lets be careful out there.  ;-)