Spraying inside tip

[Llwynog]

This is something I noticed on Ask This Old House. The segment was on replacing a stairway railing. Tom was using a spray on urethane in the house. I noticed that he had a vacuum on while he was spraying it. He was holding the hose about 4-5 inches, I think, from the surface he was spraying.

[K2!]

That would work for catching some of the stray particles of paint (or whatever the material being sprayed) but will just propel the toxic propellant gases into the room, unless the vac is vented to the building exterior. Even with a HEPA filter, the molecules of these gases are small enough to pass right through.