Usenet Newsgroups How to know when metered-inhaler is 'empty'? From: no.top.post@gmail.com These days asthma treatment commonly uses 2 different inhaled medications: 1. a long-term 'preventer' eg. Beclate; 2. a short-term 'reliever'. The reliever normally gives immediate symptoms. So you could know if your inhaler was just 'blowing air' because of the   medication being used up. But the 'preventer' gives no immediate signs. So you can't know if the med-contents is depleted. Or is the concentration of medication in the expelling-gas constant;  so that while the gas still comes, there's medication delivered. And you only discard it once the gas-expulsion is 'too' weak ? == TIA. Subject  How to know when metered-inhaler is 'empty'?  Re: How to know when metered-inhaler is 'empty'?