Paint isocyanate protection

[67rstbkt]

So, I know many of you guys are doing your own paint jobs in the garage. I've done a couple myself and am wondering what everyone is using for a respirator. I can't seem to find anything other than a fresh air system that is effective protection against the isocyanates in base/clear urethanes. I have just worn a half mask with good cartridges in the past. I always justified this by telling myself I only paint very rarely. So, what are you guys using? I'm contemplating throwing down $400 on a fresh air system. Should I?

Thanks.