Don't mix new toner every time you tone. Save your toner and reuse it, replenishing it with a little stock solution when toning times become too long.
You will need to filter the solution using a coffee filter or the like (I often use a paper towel in a funnel) before using to remove any precipitate.
This will accomplish two important things.
First, your toner won't smell of ammonia any more. Only a faint ammonia smell that goes away very quickly after replenishing.
You will use a lot less toner, saving money and not discarding a toxic heavy metal into the sewer system or your septic tank.
I keep two solutions, one weaker, one stronger, for use with different papers. They have been going for way more than ten years and tone just fine. My last toning session did not even require me to replenish the gallon of toner I was using. It had been sitting unused and unreplenished for more than a year.
Two birds with one stone.
...and do get some adequate ventilation in your darkroom
Best,
Doremus
www.DoremusScudder.com