Standard masks DON'T block the iso's.
Standard
dust masks don't protect you from iso's. But a charcoal respirator can. It has to be used, and stored properly. It does not have to be an air supplied unit.
It is complicated.
I undergo routine testing to determine the appropriate amount of exposure. This assures that my respirator is adequately protecting me. I get 25 hrs. total of use out of a disposable respirator, in up to a 7-10 day period. Then it gets changed. That falls well within the safety margins for the unit I use. That is also using it in a downdraft booth, which does a very good job of removing the spray.
Rest assured if you buy a disposable respirator, or new cartridges for a reusable one, It is very capable of protecting your lungs, for one project. It has to fit properly, and be kept in a sealed container when not being used. Once it has been used, the materials in the filters start to degrade, and in a matter of time, it is no good.
There is also a lot more to protecting yourself than a respirator. Not going to write a book here.
This stuff effects everyone differently, some get lots of exposure, and never have any reaction, and some rare cases can't even walk in the building it was used in, the next day, without a reaction requiring a trip to the ER.
I have always taken reasonable precautions, and have used it for decades without any effects. But, I have also seen dozens use it carelessly with no ill effect. I only know of one case of someone actually having harmed himself, that came after continually using it without any protection at all.