Quick thought on exhausting spray booths.

[Robert Porter]

I just had a thought after seeing a picture of someone's paint booth. Would it be possible to exhaust a spray booth safety and effectively into a large plastic tote box filled with water?

What I am thinking is if it was possible to do so without back pressure forcing the exhaust backwards towards the intakes. Not sure of the design issues but could be a solution for folks that don't have easy access to an external vent?

I am probably all wet but curious?

 

[Robert Porter]

Turns out the picture I saw was not being exhausted into water, it was a large tupperware tub filled with pink insulation and activated charcoal. The owner swears it works. No odors even when using enamels. Not too sure of the science behind that but I am going to do some digging. Anyone have any thoughts?

 

[stona]

Activated charcoal will absorb the nasty, smellies, that might be vented by your spray booth. You would have to bear in mind the amount of air the booth is passing to the filter as this would have an effect on the amount of material required to scrub it. My booth moves 355 cubic metres of air per minute, venting outside. That might need a substantial amount of charcoal to clean it.
Cheers
Steve

 

[vikingBerserker]

There is a gadget for folks that do not have a dryer exhaust setup in their home like what you described in your first post. All it does is blows the exhaust air into square bucket you fill with water. It works great for catching lint but I think it would be an issue with aerosol vapors.

I would think you could easily build something with a shop vac and filter like the one you described above.

 

[mikewint]

All paint is made up of the material that remains on the surface after the paint dries, and also a solvent that makes the material liquid so it can be applied to the surface with a brush or sprayer. It's the solvent that has "that paint smell." As the solvent evaporates, the smell becomes less and less, until it disappears completely when the paint is fully "cured." Until it's cured—which can take from days to months depending on the type of paint—the paint is slowly releasing fumes of solvent.
The toxicity of paint is indicated by the measurement of the "fumes" that come off of fresh paint, known collectively as "VOCs" (Volatile Organic Chemicals). These are gasses that are released into the air as the paint dries. Often paints contain a mix of various VOCs called "petroleum distillates," which may be any mix of solvents…whatever type has the best price on the day they are making the mix.
The US EPA has established an upper limit for VOCs in paint at 250 grams per liter (g/l) for flat finishes and 380 g/l for other finishes. Quite obviously the small amounts of paint used on the average model are much less than a Liter hence no warning labels
The paints with highest VOC levels are oil-based paints (also called solvent-based or alkyd paint). They use mineral spirits or other petroleum distillates as a base to carry the paint solids.
Water/alcohol based acrylic or "latex" paints are made from acrylic resins and various types of vinyl and use water/alcohol in place of a petroleum solvent, dramatically reducing the amount of VOCs.

OK, now the home-made filter box: First the activated carbon, a raw carbon containing material like wood, coal, peat, etc. is heated to a high temperature +600C in an inert atmosphere like nitrogen or argon. This carbonizes the material which is then exposed to oxygen or steam at high temperature. The "activated" carbon now has trillions of micro-pores giving it a vast surface area such that one gram can have a surface area of well over 1500 square meters. The exposed carbon atoms on these surfaces will attract and bind many types of organic molecules in effect storing them. The binding forces, van der Waals and London dispersion forces, are not very strong and the adsorbed gasses can be released back into the air, changes in temperature and humidity can accelerate this process. In addition since there are a finite number of binding sites the carbon can become "full" and will no longer accept more gasses.
The insulation material sounds to me like an attempt to mechanically filter out particulates of paint, i.e., overspray.
Now exhaust from his booth has to enter the box AND exit it at the same rate. Paint particulates and solvent gasses have to "flow"/pass through the insulation and activated charcoal. Simply blowing the exhaust over the insulation/charcoal will do nothing and it takes time for fumes to be adsorbed into the charcoal. Without knowing more this does not sound like a very effective "solution" to the fume problem.

 

[fubar57]

I just spray acrylics and use a pillow case over the exhaust to catch errant paint and if my wife ever reads this, I am not using a pillow case over the exhaust to catch errant paint

 

[Robert Porter]

I am exhausted outside but there are times I wish I did not have to open a window, but it works!

 

[mikewint]

Outside is always your best solution. Much like a range hood any attempt to exhaust into the room is going to fail.
With acrylics I see no reason to use any type of exhaust or particulate trap unless someone is allergic to the spray.
I use a large cardboard box 3ft X 2ft X 2ft spraying as far inside as possible. This is in my basement work room with no HVAC intakes
so I'm essentially isolated.
Glenn, if you want to isolate even more find or make a box/furnace filter combo whose dimensions match. You can find furnace filters with activated charcoal and in many different particulate size traps

 

[Builder 2010]

I'm sure you're not really using a pillow case... besides, I didn't hear anyone mention anything about pillowcases.

I'm currently lobbying to put in a nice spray booth so I can spray solvent-based paint. Being restricted to low odor paints really reduces choices regarding model finishes. I would love to work with metallic finishes, but the best are all solvent-based. I'm seriously thinking about venting outside by having a dryer vent installed in the band board. I don't want to exhaust through the window that's located nearby for a couple of reasons, one of which is drawback with using the window. There is negative pressure in the basement when the HVAC is on due to leaky ducting. I don't want to tighten that up since I rely on them to keep the basement livable in the winter.

My HVAC tech says he could install the vent for not too much money.

 

[mikewint]

Problem with those types of vents is that they "leak" air. During the winter winds can force those flapper valves open and you're going to have cold air entering an already cold basement. If you want to go that way a Dryer vent is really not that hard to install. Follow your foundation up to the outside wooden base board (usually a 2 x 10), get a 4 1/4" hole saw, locate the spot you want and drill a pilot hole to the outside then from the outside drill the 4 1/4" inward following the pilot hole. Use a high quality elastomeric or silicone calk, calk around the vent and push it through from the outside. Install wood screws to hold dryer vent in place. Go inside and calk around the vent pipe where it enters and then install an elbow. Flexible duct hose can then be used to go to your spray booth.

 

[Robert Porter]

Problem with those types of vents is that they "leak" air. During the winter winds can force those flapper valves open and you're going to have cold air entering an already cold basement. If you want to go that way a Dryer vent is really not that hard to install. Follow your foundation up to the outside wooden base board (usually a 2 x 10), get a 4 1/4" hole saw, locate the spot you want and drill a pilot hole to the outside then from the outside drill the 4 1/4" inward following the pilot hole. Use a high quality elastomeric or silicone calk, calk around the vent and push it through from the outside. Install wood screws to hold dryer vent in place. Go inside and calk around the vent pipe where it enters and then install an elbow. Flexible duct hose can then be used to go to your spray booth.

I have seen several examples of exactly that solution, it works very well with minimal if any draft. You can also mount a fan inline with the hose for extra draw, often used with furnace lines to insure the air is exhausted and not drawn back in, all depends on the length of your pipe to the outside.