How Many Fans/CFM to Ventilate Spray Painting in My Garage?

Yes i agree the box van is probably alot less, more around 250 cfm on the highest speed setting. Supply air from 1 of the HF Fans would be enough i believe.

My only concern with using a hood vent is that my painting light hangs right where the hood vent would go for best results.

Trying to move the whole amount air is what i would like to do because the fumes and harmful, spray paint is heavy, and the overspray from the paint is quite a mess.

But with the hood vent with the right amount of pressure i could pump out all the fumes before they spread into the room. Once the paint/fumes have gotten into the rooms air it would be difficult to exhaust the air through a hood vent.

Whoa up! A paint booth would have the lights on the side walls, not overhead. This helps eliminate shadows so you can see what you are doing.

You should not need BOTH intake and exhaust fans. Exhaust only should be fine, with filters on the intake side. Exhaust filters will probably get clogged with paint, but air quality regulations may affect what you use.

Im doing art on canvas/ poster boards and i wear a quality respirator while painting thanks for the suggestion to try a painting forum.

lyn,

Information first hand looks OK.

Something wrong with calculation. You can't ever remove all air from room. You perhaps dilute the air contamination and that will increase the input requirement. There must be a good calculation and some useful dispersion model for air contaminants as it is used for plume dispersion.

Of course, the flow will follow the path of least resistance through the room. The air in the corners will likely remain stagnant.

This person is using small spray cans, in a home garage. There's no need for an in depth analysis of the flow. That's why I stated twice that this was an approximation and not an in depth analysis of the room.

The OP is an artist, not an engineer.

Cheers.

Lyn,

Diffusion takes place from high concentration level to low concentration levels to have some tendency to form equilibrium. Even though this process is slow, it does play a role. How quickly we smell something abnormal disliking or pleasant smell. Somehow it reaches our nose.

Other than dilution and pumping out, there are little options to solve the problem. There are lots of aerosols which do not coagulate due to charge on their surface and they keep floating for hours. Perhaps, electrostatic precipitation may work or accelerate the decontamination process.

I hate dust particles in air and I avoid roads that have lots of dust flying around. It causes allergic reactions. Some paint may also have Radioactivity which may become body burden. We used to scan people on whole body counting system to see if they have enough radioactivity already in the lungs from paint they used and from other sources of leaked out radioactivity.

I have seen some people painting in open space and so much paint sets on them that they take bath in some thinner - paint dissolving fluids. I think there is a lot of professional hazard in this work.

Good luck.

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if you really want to do it right (not cheap) you can use this as a guide. it has the formulas you're looking for + morehttp://www.sdcounty.ca.gov/deh/food/pdf/publications_ventilationguideline.pdf

Thanks for the link, but this setup is a little out of my price range but a very good setup indeed. My budget cuts off at around 500 for all 3 fans ill need to pump in and out air

good luck

You haven't really told us much.

Is this going to be an ongoing enterprise? If yes, cheapin' it out will only prove problematic with quality and volume of finished work.

If a one or two shot deal, you can get a real painter with a real live legal paintbooth to do these for you. This not only frees up the garage for your car, but the finished projects will (likely) turn out nicer.

As other members have said, it sounds like this is a more involved project than you believe it to be. I understand that you want to do it yourself... wait, is this some sort of group project... boy scouts, church group, something of that sort?

Yes iam painting canvas/psoterboard and had nothing to do related to cars or painting them. I sell these paintings and it will be ongoing thing as long i can make sure i dont breathe in fumes.

Didn't get out fast enough. Look at these, and take it from there:
Building a small fume hood for stinky projects
How to Create a Paint Booth in Your Garage: 12 Steps
Good luck, now I'm gone.

You don't need to vent the entire room.

Do some reading, and searching.

The hood form is too constricting and the paint booth would be the entire size or my garage but thank you for the suggestions

Any more ideas out there for where to purchase ventilation fans?

If it was me I would invest in a propane or diesel powered Jet heater and set that up to draw the fresh cold air in from outside heat it and blow it into the garage and then have a fan or open window that can let the air out of the garage.

That way you are replacing the air in the garage with warm air and purging the old air out.

Given your small garage space a 30,000 - 50,000 BTU jet heater would be plenty big and provide more than enough of an air exchange rate.

If the temperature is so low outside that the paint doesn't dry, simply force-ventilating the garage will make no difference.

The simplest and lowest-cost solution is to spray with the door open in warmer weather.

Look into the new water based products. If they work, you can get by with a particle mask. No ventilation necessary.

http://toolmonger.com/2007/04/18/krylon-puts-latex-in-a-rattle-can/

These guys have 100 colors. Sounds worth looking into.

http://www.liquitex.com/spraypaint/

Most paint booths will use infrared lights to heat. Infrared light will heat the surfaces first and not the air which in a paint booth is being remove by ventilation. You will have to provide enough infrared lighting to maintain a working surface temperature for the paint to dry properly.

Which will be a balance between the volume of air need to ventilate and the outside temperature.

The installation needs to be done to explosion proof specs for safety.

DreamCoat-

Simplification of your problem---> You don't need to vent the complete garage, you just need to get rid of the vapors from the paint propellants in the cans as you paint. Unless you are using multiple cans at the same time this quantity isn't hard to remove. The equipment you have now, with a little more is sufficient. You only need to remove the concentrated vapors, not disperse them into the whole garage and then have to vent the whole garage. If necessary, this can also be incorporated with a slightly modified spray booth.

Tape or make a holder for a 20" x 20" furnace filter to be located on the suction side of the box fan. Place this, filter towards the location of the painting, in front of a window or door. Place object to be painted in front of fan, turn fan on and adjust speed to as fast as possible without distorting the paint as it is applied onto the object. The paint/vapors/air are pulled towards the fan, atomized paint is removed by the filter so it doesn't foul the fan, vapors/air are drawn through fan and are dispersed to outside the building. The vapors are mixed with the air and dispersed at a very low concentration so if they are flammable they will be much lower than the LEL.

Caution- As the ambient air is drawn out of the building, the air within it is going to get very cold if the outside make-up air is cold. If you are doing this for a long period in a cold location wear warm clothes.

By placing this apparatus on a table the objects can be painted easily. Also a "Lazy Susan" type apparatus increases the convenience.

It works for me. Not only do I do it in the garage but also in front of a door in the basement. No complaints from the wife upstairs about the odor, except when I come up with paint spray on me from touching the wrong things.

Good Luck, Old Salt

Wet the floor with water to trap the particulates and hose them out when you are done. This will settle the dust as well.

Rather than use a paint hood you could use an extraction table. Paint over the table which usually has a heavy mesh top covering the opening of the extraction fan. Between gravity and your fan the paint over spray and fumes should be largely contained. You can still use your light to see what your doing while cutting down a lot on the fumes. I'd still be wearing activated charcoal filters on appropriate breathing gear though. And yes definitely some filter on your extraction fan to trap the over spray or you won't be popular with your neighbours if it floats over their cars or clothes on the line.

Thank you for the reply Old Salt, you have been the most helpful.

I'm using 1 can of paint at a time, no longer then 20 mins at time. Max 2 spray cans at once but not very often. Then i let the room ventilate before i continue to paint. To ensure that i am bringing in enough clean air

The intake fan i have is coming from the warm house and not the cold outside. So the the new air coming in is warming my room while the room in ventilating.

As you can see in the picture i have the painting table (the one with the computer on it) in front of the garage door to the right of the window.

So if your saying i were to put my painting table right under the wall closet to the fan it should be powerful enough to pump out the amount of paint im spraying?

where I used to work, the shop guy made a booth.

Picture a sheet metal box that's about 24" H x 36 W x 24"D on rollers with an open front and a large furnace filter for the back. Now put it on wheels.

The door opened downward, so you could paint on that for larger objects and the door was held up with a chain.

Inside there was one incadesent explosion proof lamp. Definately not the best lighting.

We then had the ability to exhaust the "exhaust of the booth" with an extraction arm like this one: http://www.nederman.com/products/extraction-arms/welding-fume-extraction-arms/original-welding-fume-and-dust-extraction-arm

So, if the items are not that big, make a booth.

Aside: Why cans. If you do a lot of painting, why not a paint sprayer?

DreamCoat-

The fan you currently have is called a table fan. These often oscillate sideways to force air in a wider area. They do not have much air speed and are used to circulate air in a room. What you should use is called a "box fan". This is a square unit, about 20" on each side, and pushes air in one direction. Most of these are equipped with a three speed motor controlled by a multiple position switch, off-low-medium-high. This unit will move 2,000 cu ft. of air per minute. They are available at HD and Lowes among many others, for about $20.00 and upwards.

Low cost glass fiber hot air furnace filters are also available there. Purchase a 20" x 20" one and some masking or duct tape. Tape the filter to the suction side of the fan. This will remove any airborne paint thus helping keep the fan cleaner and a longer life. This will be dirty as the fan is used, but this is good. The more it loads up the more you are filtering out.

The picture indicates that the fan can be located in either of two places, in front of the window or the garage door. If the window can open and has a screen on it the window can be opened and the fan mounted or placed there. If this is possible you might want to consider an adjustable window fan instead. The fan, no matter which kind, is to be mounted with the suction side towards the inside. The screen helps keep flying and small walking visitors out

If this is not practical the garage door can be used. The least effective is to open the door just enough to place the fan under it. The fan is then used by turning it on. You didn't state where you live but if it is cold it would be good to block the other open area of the door. Plastic sheet, cardboard sheet, 1/4" plywood, Masonite sheets or even available cardboard boxes will do.

The closer you paint to the suction of the fan is better. With the speed adjustments of the fan try to run it as fast as possible. When using this check for overspray and increase the fan speeds if possible.

To operate, turn the fan on to a suitable speed, place the piece to be painted on the table and commence painting. If you doing much of this aerosol painting it is easier to use a trigger grip can holder than to hold the can directly in your hand.

Good Luck, Old Salt

Effectively wouldn't you just need to extract the same volume as the can of spray can produce.

Your house has at least two ready to go spray booths in it already.

Do the painting in your kitchen or bathroom. These would have adequate ventilation for your purposes if you turned their extractor fans on.

But check with the wife first !!!

....never get anything done if you go down that path.

So what i get from this is that you are a "Tag Paint artist" and you use the garage as your studio. I think first and formost before figuring out the venting are you in a rural area or are the neighbors right next door and are they going to like the fumes.

You may be better off leasing a studio with adequate ventalation for your trade.

You would have to be crazy to paint on your stove or in your bathtub.

OldSalt, i do have a box fan in the window its just hard to see because the light in the photo. The oscillating fan is not in use. That is what i had then last year. The furnance filter idea is really good thank im going to do that for now but i would like to get a stronger system.

I live is BC so its very cold here i cant open the garage door but if i plywooded it off like you said that would work. But its better to have the exhaust above what your painting on.

Dreamcoat-

I sounds like your fan might be starving for make-up air. If the intake fan is appreciably small than the exhaust fan this would cause that. You say you are in British Columbia so it gets cold out. A very insulated house would not help because the is very little leakage to accompany the intake fan air. This would be accentuated during the colder months since the intake fan may not have enough air to give the exhaust fan, especially if it is only providing air that originated within the house. This is not an unusual situation for this type of fan and usage. During the winter you may have to give up some of the heat and open a window or door for makeup air from the house.

Otherwise there are a few alternatives. If window space provides it, put two fans side by side for exhaust. At 2,500 cfm each and filter loss of 500cfm for each fan that will be a total of 4,000 cfm. For a 20'long x 20' wide x 10' high double garage that is one complete change of air per minute. That's a lot of air exhausted and it requires a lot of make up air. With one fan you have one air change every two minutes.

As a trial make up a light weight spray booth about 30" wide x 30' deep. make it high enough to go as close to the fan as possible. The side facing you will be open, the left and right sides will be solid and the back open on the approx. upper half. With this set up most of the exhaust air comes from through the booth, just where you want it to be. Place the objects on the bottom of the booth and paint them there. Add an old lazy-susan or something to that fashion to rotate the piece. If you can conceptualize this go ahead and make it. This is what I did for my first spray booth but I used either a carton from a washer or dryer for the booth. If you know someone who will be getting a new appliance let them know you want the box. You can't beat the price for a test unit.

As a air velocity test, run the system as you always do. See what the air velocity is, a visual approximate test is ok. Small ribbons or tell tales from a sail boat will make this easier to tell. Next open the garage door half way and duplicate the air velocity test. If you notice other than a minor change you are starving for make up air. If you or someone else smokes cigarettes, or a fine cigar, have them stand about 3-4 feet from the exhaust fan and duplicate this test. The cigarette makes it easier to visualize the speed of the air difference. Repeat this for the make up air fan.

If there is a large difference in the two air exhaust or make up velocities you need more make up air. Remember with even one box fan you are changing the air every two minutes. That's a lot of air to make up.

Adjust the fan speeds to give you the best air speed. Too fast and the paint will be pulled around the object and not get onto it's surface. Too little and the excess atomized paint will not be exhausted or mar the painted surface.

The order I would do the tests would be

Air velocity tests at exhaust fan

Air velocity tests at make up air fan

Box booth

Adjust fan speeds

At this point this cheap process of deduction should determine what the problem is. If not let me know.

Good Luck, Old Salt

Thank you for all the help! my painting setup is alot better now

I moved my table right under the fan and it vents out the room alot faster and more efficient.

But my only problem is now the window is too high and some of the paint is still getting into the room instead of people straight ventilated.

The fan is roughly about 2.5' above the table and it pump alot of flumes out but this work much better if my window was lower and the fan was closer to were im spraying.

any suggestions?

DreamCoat-

Congratulations on the successful installation! Glad to hear you took the efforts and the "paint booth" is working.

There are a couple of solutions for getting the fan closer to where you are spraying.

1) put the table higher so it spays in front of the fan. Of course this would also require several height adjustments including probably painting from a ladder. Quick but not convenient.

2) Use a section of approx. 20" diameter air conditioning flex duct to connect the inlet of the fumes/paint to the fan at the window. Quick but expensive.

3) Similar to the plenum on a forced air furnace discharge, make a sheet metal/wood/cardboard duct that fits between the discharge of the spraying and inlet of the fan. This could be anything from a gradual slope up to the fan to a periscope shaped duct. Use as big of dimensions as possible so as to not starve the fan. I would start designing by taking some corrugated cardboard sheets from boxes or boxes themselves and a roll of duct tape. Fashion is so it starts at the spray area and ends in front of and connected to the fan inlet. This device does not have to be round or any special configuration. Just make a duct from the spray area to the fan.

Once you have gotten a configuration and size you like, then make it out of 1/4" plywood or similar material with cleats at the corners for attaching adjacent sheets. This could also be fabricated out of sheet metals if you have the tools to work with it or have a shop make one for you based on the cardboard test piece. Any good sheet metal shop should be able to use the cardboard model as a guide.

Personally I would start with the test configuration of corrugated cardboard and duct tape. Gives me the chance to try out many alternatives and it doesn't cost much. Once that was done I would decide what I want to make it out of based on the usage and costs.

USE YOUR IMAGINATION, try different alternatives.

Good Luck, Old Salt

I also have a question; even with a filter before the fan, will the exhaust coming out of the "paint booth" have enough particles of paint that you would have to worry about cars, concrete, etc. outside? I was thinking about making a temporary booth in my garage but the only outlet I have would be thru the garage door opening. Would I have to worry about paint on the concrete outside the door, or any cars parked nearby?

Depends on how far away the cars from your exhaust fan. Concrete i wouldnt really worry about unless its right close to another house. I have one of those thick blue course looking furnace filter and its enough for me because i have a good nothing directly in front of the exhaust.

If you are more concerned i would buy the nice thick furnace and put that either in front or behind the exhaust it doesnt really matter. But you should have extra protection if you not using a in closed motor. Because it will, sooner then later, destroy the motor. I have a 20" box fan with furnace filters in front of it to protect it from spray and it works great.

Just remember though, the more clean you wanna be with sprays outside just increase the filter quality/thickness etc. This will work fine, and if you wanna use you garage door as a opening:

Lower the garage door to the size of your fan then put quarter to half inch plywood to block the cold and cut out of the plywood where the fan is going to be exhausting. Then seal everything off etc etc. But if the fan is at the bottom of the garage it will only exhaust the fumes falling down from the table rather then the fumes floating up. Im personally more concerned about the fumes staying in the air range where you are breathing rather then the falling fumes.

but if your only possibility is by opening the garage door , that is the best you can do and i wouldnt make it any more complicated then that. this is the cheapest, and most efficient way to exhaust your garage it should work quite well i just havent tryed this method.

Where a good quality respirator with organic vapor cartridges and make sure there fairly new, like not over a couple months old and keep changing the pre filters as needed

Use the glass matt type filters used in forced air furnaces to filter the return air. It is also wise to double them up so that the paint/vapors/air go through 2 filters in series. To check if there is paint making it through the filters simply look at the discharge side of the filters. If there is no paint there no paint is getting past them. I use my "spray booth" in my basement in front of a door to the outside and never had any problems with overspray if the fan is operating at a sufficient speed. A 20" utility fan puts out more than 2,000 cfm when set on the highest speed.

Good Luck, Old Salt

Thanks. Good comments from what appears to be somebody that has done it before. That was what I needed.