: This is a couple steps ahead of where I am, but I want to get ahead
: of potential problems.

: I realize dusty environments are bad for varnishing, but are they
: also bad for fiberglassing? I'm building in a woodshop that
: doesn't have a system from removing dust from the air, and I see
: that when I set my phone down flecks of sawdust show up on the
: screen after I come back to it a few minutes later.

: This place is gigantic and used by others, so "just clean
: up" isn't a viable option. I could glass it elsewhere, but
: if that's the case I need to start planning now.

You can isolate yourself from the dust by making an enclosure of plastic.

Screw or clamp some 2x4s to the ceiling joists and floor and tack plastic around your
boat to make a work area. If your plastic won't reach all the way from floor to ceiling
hike it up to the top to stop the lighter dust.

A half hour before you work, wet the floor and mist the air with a plant sprayer.

This will work for your epoxy and for varnishing.

You can varnish outdoors. The marine spar varnishes we use are designed to be used on
boats moored on the water.

Pick a morning after it has rained. The rain will have cleared dust and pollen out of the air
like misting your shop with a plant mister.

Varnish in the shade. On a porch or under a canopy is good. Direct sun will make your varnish
"set" too fast and you will have brush strokes visible.

If you are near water sources keep an eye out for a bug "hatch" where thousands of new
flying crawlys may land on your boat.

Applying epoxy outdoors is very risky because if the sun hits the epoxy it will cause it to thin
and run off and any wood not already sealed will off-gas bubbles like a volcano.

Everyone working with epoxy should coat a piece of wood and place it in the sun to see what
off-gassing is like. The same thing will happen if you have spot lamps or other heat sources
close to your boat in your shop when you're coating wood.

All the best,
Rob