I like the 3M disposable 4000 series half masks.
They do me a least a month of diy use, if kept sealed in the supplied bag.
They have the same or better filters than the blower unit thats the norm now and they fit under my mask fine.
I also use them for grinding and other dirty stuff.
Only problem is they seem tp have gone up in price since Covid kicked in.
Zoro do a pre filter that saves the main filter from very dirty conditions.
I use a 3M 6000 series half mask with 6055 filters and 5953 pre filters. Kept in sealed bag it lasts me a month or so of heavy use, a couple months if only using every now and then. Good for rattle can spraying too
Working at Appledore shipbuilders ltd during the 90s, we were issued what we referred to as a "twin air" respirator, this respirator consists of a rubber mouth and nose piece, held in position by straps over the head, exhaust air exited via a one-way valve near the users mouth: inhaled air came via two hoses, that went over the shoulder to a filter box at the small of the welders back, this was kept in position by use of a belt:
The advantages were, the filters were very easy to change, and there were various filters dependant upon your need:
A very basic design with no electrical or moving parts
Easy to clean and robust
They did work very successfully
They had a long life expectancy
There are several drawbacks, the mask is quite bulky, necessitating the use of quite a large welding screen, ASL issued 'long shell' screens that were fitted to your safety helmet, a measure introduced after several welders had serious 'arc burn' on their throat and neck areas, but they do fit under most traditional welding screens
They can be hot, sweaty and feel as if it's slipping off
I don't know whether they're still available, or where to source one, a very good piece of PPE, that did EXACTLY what is was designed to do