What kind of respirator do I need to safely work with varnish, polyurethane, and oil-based stain?

Question

I like building small projects for around the house, but I don't like exposing myself to the harsh chemicals of finishes.

What sort of respirator will give me protection against these chemicals so I can safely work with them?

Answer 1

For normal chemicals and finishes, most tradespeople will wear a half mask (3M are readily available and popular) with an OV (organic vapor) cartridge and at least P95 filtration. (Filtration since you mention the "building" part of small projects.)

You need to size them to fit (fitting instructions come with units -- generally, you should be able to plug the ports and not have the mask leak).

You can get ones with replaceable filters and ones that are non-replaceable. Prices vary, but I imagine the initial cost of the non-replaceable is lower, but of course they become landfill after the cartridge is done.

If you get into more obscure chemicals/acids/ etc, you'll (almost certainly) be able to find a replacement filter that'll suit the application.

Edit, to address lifespan… turns out, it’s complicated. This, from 3M, seems sensible, if perhaps (understandably) careful. 3M doc on OV reuse

Answer 2

Since this will become our main respirator Question that we'll link to in future, I thought it would be worth adding a sort of frame challenge to the idea that respirators are needed to safely work with varnish and other oil-based finishes that contain mineral spirits.

While respirators are very advisable for the casual user doing certain tasks (enclosed spaces, long exposure) and may be mandatory for users working around the finishes occupationally, there are other ways you can obviate the risk from working with high-VOC finishes that you can use some or all of the time depending on your circumstances and climate.

These include:

• doing the work outdoors¹;

• working in a very well-ventilated space (porch, gazebo, large garage or shed);

• arranging active ventilation — airflow past the user, then the workpiece/open containers of finish and then outside, e.g. by placing a box fan in an open door or window;

• choose to dilute, rinse brushes and clean up using odourless mineral spirits.

Or.....

Use something else
Obviously another option is to use low-VOC and no-VOC finishes instead. There are some traditional choices here, as well as an increasing number of modern finishes to pick from, including:

• linseed oil or another drying oil;

• wax could be a low-VOC or no-VOC option, but the usual formula for commercial paste waxes does contain a noticeable amount of spirits;²

• shellac, while technically a high-VOC finish as commonly used the fumes are considered basically harmless since they can consist entirely or almost entirely of ethanol;³

• waterbased products, which have gotten better and better over the years;

• and most recently, the so-called "hard-wax oils", many of which are classed as zero-VOC.

---

¹ This might seem crazy with slow-drying finishes and the risk of dust, but oil-based stains are typically wiped off to leave a practically dry surface and varnish can be diluted and applied very thinly, with all excess wiped away, making dust almost irrelevant — you can literally sand wood in the same room that projects finished in wiping varnish are drying, without concern you'll ruin the finish.

² Possibly not enough to be any sort of real hazard for the occasional user, but the smell could still be bothersome for anyone sensitive to it.

³ Shellac can also be made to be a zero-VOC finish by dissolving it in an alkaline water solution instead of an alcohol.