Will varnishing indoors present explosion hazard

lacquer

Bill Tindall, E.Tn.

Lacquer solvent has a lower molecular weight so it takes significantly less grams per air volume to reach its LEL. And it volatilizes much faster to challenge room air turnover. I have no doubt that painters who smoked while lacquering indoors didn't reach retirement age.

Re: lacquer

Jesper, Denmark

Generally speaking, Bill, it is very unpleasant to be in a room with anywhere near the LEL af HC solvents. Hence, as a rule of thumb, if it just smells a bit, but is not eyewatering to be in the room, the chances of being anywhere near the LEL is very small.

A better experession is really LFL, Lower Flammable Limit, as the combustion is not with a flame front anywhere near an explotion.

So, ventilate till it is a comfortable atmosphere to work in, and the only place near the LFL is just over and in the open can.

agree, correction, in addition- important folloup

Bill Tindall, E.Tn.

It is true that the LEL is greater than a concentration of vapor one would tolerate working in. But a LEL could exist where your nose isn't. That is the danger.

Lower flammability limit, LFL, and lower explosion limit, LEL, are equivalent.

"and the only place near the LFL is just over and in the open can."

While the container one is working from is a potential source of LEL that is not the area of greatest evaporation rate. The greatest rate of flammable vapor generation is at the application site. Not so much with a slow evaporating solvent like mineral spirits, which is why mineral spirits is used instead of naptha. But the application site is a significant risk with fast evaporating lacquer. Spraying generates a higher rate of vapor generation than brushing.

Another concern is the heavy flammable vapor sinking into a poorly ventilated area and concentrating.

Bottom line, the good ventilation needs to be where the application is occurring.

Re: lacquer

Barry Irby

Several decades ago I was a builder. I pulled up at one of my houses only to see the floor finishers swirling around like angry bees. Turns out the house had about 300 sf of hardwood and they had applied a coat of lacquer. Padded on a liberal coat. The plan was to wait a while and put on a second coat. They liked lacquer because it dried quickly and they could do two coats in a morning. They had all the windows open. Somehow the fumes found an ignition source and it went BOOM. Boom maybe and over statement, more like foom. Kind of like when the cook flambes the cherries jubilee. It was over so fast they did not even have time to foul their pants. They buffed the floor and applied another coat and the floor served its purpose for about ten years. Then we moved some walls around and patched it and refinished it. Appeared to do no harm, other than to make believers out of the floor finishers.

When I apply finish in my shop I leave the DC hose nearby and run it to remove as much of the fumes as possible. The exhaust goes out side and the motor while not explosion proof is TEFC.

Nothing like a good illustration

Re: lacquer

Hank Knight

There was a young local man that had become a very good at reconditioning pianos. He had a small shop where he worked alone. About 20 years ago he was refinishing a piano and spraying lacquer in his shop. Something ignited the ambient lacquer solvent; the speculation was the pilot light in his water heater was the ignition source. There was a terrible explosion that wrecked his shop. He was severely burned and died from his injuries several weeks later.