dewitteridder Posted March 19, 2014 Report Share Posted March 19, 2014 Marc, Matt, and Shannon covered this question on a wood talk episode not too long ago. From the episode they mentioned that the fumes may be heavier than air so when you are below grade you need to really keep that in mind. If you're pull the air from up high it won't necessarily clear the fumes from the area if all the fumes are collecting near your legs. I'm not an expert and it seems like a lot of people who have responded have had more experience. I thought I would just chime in with my 2 cents. Sometimes it is also just better to wait to do it during the warmer months. Your health should be the highest priority. =) Quote Link to comment Share on other sites More sharing options...
Jfitz Posted March 19, 2014 Report Share Posted March 19, 2014 please check my numbers. 100cfm per sf of cross sectional area means that approximately 1.67CF of air will pass through a sq ft of cross sectional area every second. Or, the air would be moving at about 1.67 linear feet per second through that cross sectional sq ft. I can see that being a noticeable airflow but not enough to disrupt the flow from an HVLP. it's the equivalent of about a 1.14MPH breeze. For a 10wx10'h finishing room (100 sf cross sectional area) that comes to 10,000 cfm. Quote Link to comment Share on other sites More sharing options...
AceHoleInOne Posted March 19, 2014 Report Share Posted March 19, 2014 Have you ever used a spray booth?? Exhaust fans dont create a breeze that is not how a spray booth works. No it wont affect the finish nor will it pull the finish away from the work surface. Here is one that is actually smaller than the proposed 10x10 in fact half the depth. http://thefinishpro.com/store/product.php?productid=16172&cat=263&page=1 Here is the one Im ordering that is running 12000 cfm and is closer to the proposed 10x10 http://thefinishpro.com/store/product.php?productid=16224&cat=263&page=1 Both just barely meet legal limits most shops run much higher cfm rating. to create any sort of breeze in a 10x10 booth with an exhaust fan you would have to push it up over 24000 cfm. Spent my early days in a paint spray booth. Don't know the CFM rating had 2 large exhaust wall fans. Later the place had a fire then was upgraded to a huge filter wall. In those days we didn't run the fans while painting due to airborne contamination issues. Only ran the fans after the paint tacked-up to clear the room which didn't take long at all. Perhaps 5 minutes. Every spray room I have been in you can feel a breeze. That air has to move to clear a room. Fans create air movement. Too much air movement causes a breeze. Again the formula is how many times the air changes out per-hour or minutes. In the home shop spraying water-borne in a enclosed 10x10x8 room doesn't require 6450 CFM and is over-kill in my little mind. And it's my little mind. -Ace- Quote Link to comment Share on other sites More sharing options...
Jfitz Posted March 19, 2014 Report Share Posted March 19, 2014 So I "get" the filter component to trap overspray particles before venting outside, but are there any filter options to trap the fumes (e.g. from lacquer) as well? Quote Link to comment Share on other sites More sharing options...
AceHoleInOne Posted March 19, 2014 Report Share Posted March 19, 2014 So I "get" the filter component to trap overspray particles before venting outside, but are there any filter options to trap the fumes (e.g. from lacquer) as well? Poster only sprays water-based. Do not spray solvent of any kind in the house! End of Story! The filters protect the fans from getting fricked-up and coated with paint/stain/topcoat and our glorious environment stays clean. -Ace- Quote Link to comment Share on other sites More sharing options...
dwacker Posted March 19, 2014 Report Share Posted March 19, 2014 Again the formula is how many times the air changes out per-hour or minutes. In the home shop spraying water-borne in a enclosed 10x10x8 room doesn't require 6450 CFM and is over-kill in my little mind. And it's my little mind. -Ace- Its very clear its 100cfm per sq ft of face opening and NO you should not feel a breeze in a spray booth unless your in a powerful downdraft automotive booth. In fact spraying with the exhaust fans off is illegal and dangerous in ANY commercial shop water based or not. In fact you legally have to have a solenoid valve that cuts your hvlp air supply when the exhaust fans are not running to prevent people from spraying with the fans off. And yes you can spray solvent provided you have the proper airflow and fire prevention meaning explosion proof exhaust fan and lighting. Quote Link to comment Share on other sites More sharing options...
AceHoleInOne Posted March 19, 2014 Report Share Posted March 19, 2014 Its very clear its 100cfm per sq ft of face opening and NO you should not feel a breeze in a spray booth unless your in a powerful downdraft automotive booth. In fact spraying with the exhaust fans off is illegal and dangerous in ANY commercial shop water based or not. In fact you legally have to have a solenoid valve that cuts your hvlp air supply when the exhaust fans are not running to prevent people from spraying with the fans off. And yes you can spray solvent provided you have the proper airflow and fire prevention meaning explosion proof exhaust fan and lighting. Well we agree to disagree. This is a homework shop using water-based in the basement for casual use. Having a small 10x10x8 enclosed spray room to achieve a high quality finish. Don't know why you would want that much air flow. Wood shop are dusty and having an open-face booth pulling in that much air makes no sense to me and getting crap in your finish isn't worth it to me. Peace - out! -Ace- Quote Link to comment Share on other sites More sharing options...
Tpt life Posted March 19, 2014 Report Share Posted March 19, 2014 Water born being fume free is a semantic farce. Read MSDS for your water born stuff and they still do nasty things to your lungs and pores when atomized. While you have incredible latitude in some states with regard to safety in your home space, dealing with explosive or potentially harmful atomized sprays is well worth whatever caution you can give it. That said, the standards set are high. This is intentional to avoid any situation that can draw on your liability. You can get away with a lot...until you have an unrelated fire and your insurance company finds a spray booth in your basement. Please weigh the cost very carefully. Quote Link to comment Share on other sites More sharing options...
Marco Divetta Posted March 19, 2014 Report Share Posted March 19, 2014 Franklin ... What size projects will you be spraying ? Your planing a 100sf footprint with an 80sf opining at one end .... That's a big space, on your original post you have a few small pieces on a bench. What if you made a hood that sits on a bench 5' long 4' high and 5' deep that's ducted directly to the window, a 5' X 4' opening with a fan drawing 1200 cfm will give you air moving at 60 fpm ( without a filter ) which is a lot better than the 15 fpm you'd get with the 10' X 8' opening Just spray your piece then pick it up an move it to a drying area in another part of the room, the negative air pressure created in the hood should contain a lot of the particles and if you put the fan low in the box you won't be fighting gravity. Just an idea Quote Link to comment Share on other sites More sharing options...
AceHoleInOne Posted March 19, 2014 Report Share Posted March 19, 2014 The Idea of an enclosed room, I think works best. At floor level on each side wall, cut a 20x20 opening and cover with a furnace filter. Exhaust off the upper back side. If you need more air movement. Simply open the spray room door. By having an enclosed space, less air to clear. Open face booth is really sucking a large quantity of air because the booth has one wall missing. Hence the need for a huge CFM fan. -Ace- Quote Link to comment Share on other sites More sharing options...
dwacker Posted March 19, 2014 Report Share Posted March 19, 2014 I think if your going to give advice on safety it should be somewhat close to the truth. We all do things that are not safe in our own shops but I generally would not suggest that someone do what I do. The fact is that there are rules for a reason. Using these as a guideline is just plain good common sense. I spray loads of solvent lacquer and stain with no fans running but use box fans to clear the shop this does not make it right or safe in fact its probably killing me, thus I would not suggest that anyone do it. Enclosed booths just like open face require the same amount of air to clear the booth. The only difference is where the air comes from. In a dusty woodworking space the booth would have doors but the doors have tacky filters to collect any dust. The doors are just filter frames. The air intake space is exactly the same. You can't just put in less air intake space and assume you need less cfm to clear the room. There is no such thing as a selective exhaust fan that only takes in contaminated air. It does not matter if its a hobby shop that sprays once a year or a busy factory it still takes the same cfm to clear the space. To calculate the amount of exhaust air needed for the booth, a simple calculation is used. CFM = Booth Face Area in square feet multiplied by the required flow (typically 100 FPM) For example, and 8 X 10 filter bank (80 square feet) would require an exhaust of 8000 CFM (100 X 80) to achieve the required 100 FPM velocity. To calculate the existing velocity knowing the exhaust volume the following formula is used: Velocity = Exhaust in CFM divided by the booth filter area. For example, a fan that exhausts 9000 CFM with a 10 X 10-filter bank would have a velocity of 90 FPM. Proper airflow is not only necessary for the protection of the operator, but is necessary to achieve the desired finish quality. Flow that is too low will not draw the overspray to the filters. Much of the overspray will end up on the part as dry spray (rough finish). If the flow is too high, solvent tend to evaporate too quickly resulting in dry spray. Quote Link to comment Share on other sites More sharing options...
AceHoleInOne Posted March 19, 2014 Report Share Posted March 19, 2014 PB... you spray solvent lacquer in your house and use box fans? -Ace- Quote Link to comment Share on other sites More sharing options...
wtnhighlander Posted March 19, 2014 Report Share Posted March 19, 2014 PB's arguement makes sense to me. Have to bear in mind that the air going out is made up of a MIX of the contaminated air AND the fresh air coming in. I have no experience with which to compare the math, but it makes sense that you need more flow that the simple room volume.Oh, someone mentioned earlier that filtration is important to protect the fan or blower. This is absolutely true. Airborne particles of finish can and will gum up the fan motor, greatly increasing the risk of an electrical fire, even if the finish is not flamible. Quote Link to comment Share on other sites More sharing options...
dwacker Posted March 19, 2014 Report Share Posted March 19, 2014 PB... you spray solvent lacquer in your house and use box fans? -Ace- If I had a spray booth in my living room moving the right amount of air I would have no problem with it. My shop is detached. Quote Link to comment Share on other sites More sharing options...
dwacker Posted March 19, 2014 Report Share Posted March 19, 2014 PB's arguement makes sense to me. Have to bear in mind that the air going out is made up of a MIX of the contaminated air AND the fresh air coming in. I have no experience with which to compare the math, but it makes sense that you need more flow that the simple room volume. Oh, someone mentioned earlier that filtration is important to protect the fan or blower. This is absolutely true. Airborne particles of finish can and will gum up the fan motor, greatly increasing the risk of an electrical fire, even if the finish is not flamible. It really not something I made up nor is it an opinion. Its very well documented and nothing new. Also furnace filters are not the right kind of filters they block to much air. Booth tacky filters are cheap and work properly. Quote Link to comment Share on other sites More sharing options...
Marco Divetta Posted March 19, 2014 Report Share Posted March 19, 2014 Usually The problem with air not moving fast enough is the particles of finish in the air have time to stick to the wet surface resulting in a rough finish, in most of the open face booths your spraying close to the filter where the air is being drawn in so the particles are gone before they have time to dry, that's why I suggest spraying under an easy to build hood and then move the piece.... And all this isn't even taking into account any volatile fumes you might be spraying into the air !!( I know this isn't the case with Franklin but you never know what tomorrow brings )... I'm not sure how much air is pumped out of a spray gun but if I'm pumping out 100cfm of a harmful and possibly volatile gas I want to get rid of it just as fast specially in a closed booth. And please I'm by no means a professional on this stuff I'm just trying to remember things from a previous life Quote Link to comment Share on other sites More sharing options...
rodger. Posted March 19, 2014 Author Report Share Posted March 19, 2014 Thanks for all the replies guys, it seems maybe my original idea is not so good. What if I reduce the size of my spray area, like was suggested above? Would that allow the furnace fan to expel enough air to make it safe? I don't want to be risk my health of my family for my hobby. Quote Link to comment Share on other sites More sharing options...
rodger. Posted March 19, 2014 Author Report Share Posted March 19, 2014 Franklin ... What size projects will you be spraying ? Your planing a 100sf footprint with an 80sf opining at one end .... That's a big space, on your original post you have a few small pieces on a bench. What if you made a hood that sits on a bench 5' long 4' high and 5' deep that's ducted directly to the window, a 5' X 4' opening with a fan drawing 1200 cfm will give you air moving at 60 fpm ( without a filter ) which is a lot better than the 15 fpm you'd get with the 10' X 8' opening Just spray your piece then pick it up an move it to a drying area in another part of the room, the negative air pressure created in the hood should contain a lot of the particles and if you put the fan low in the box you won't be fighting gravity. Just an idea The largest projects I will be spraying are probably typical cabinets and bookcases. I suppose I could prefinish parts of necessary. Quote Link to comment Share on other sites More sharing options...
rodger. Posted March 19, 2014 Author Report Share Posted March 19, 2014 Marc, Matt, and Shannon covered this question on a wood talk episode not too long ago. From the episode they mentioned that the fumes may be heavier than air so when you are below grade you need to really keep that in mind. If you're pull the air from up high it won't necessarily clear the fumes from the area if all the fumes are collecting near your legs. I'm not an expert and it seems like a lot of people who have responded have had more experience. I thought I would just chime in with my 2 cents. Sometimes it is also just better to wait to do it during the warmer months. Your health should be the highest priority. =) Can you recall the episode number? I have listened all the previous 10 episodes, but must have missed it! Quote Link to comment Share on other sites More sharing options...
dwacker Posted March 19, 2014 Report Share Posted March 19, 2014 Thanks for all the replies guys, it seems maybe my original idea is not so good. What if I reduce the size of my spray area, like was suggested above? Would that allow the furnace fan to expel enough air to make it safe? I don't want to be risk my health of my family for my hobby. At 1200 cfm if you go by the standards you can have a 3 ft by 4ft so if your very short person it will work fine. Spray booths are not complicated. There is loads of bad information but there is equal amount of good info to be had. Binks, compliant and any other booth manufacturer has plenty of info on their web sites that will help you put together a booth and you can do it on a budget. You may not get the smooth metal walls but even drywall is better than nothing. 1 Quote Link to comment Share on other sites More sharing options...
Marco Divetta Posted March 19, 2014 Report Share Posted March 19, 2014 At 1200 cfm if you go by the standards you can have a 3 ft by 4ft so if your very short person it will work fine. Spray booths are not complicated. There is loads of bad information but there is equal amount of good info to be had. Binks, compliant and any other booth manufacturer has plenty of info on their web sites that will help you put together a booth and you can do it on a budget. You may not get the smooth metal walls but even drywall is better than nothing. I'm sorry I keep saying this but what about a 3' X 4' hood on a bench ???... It just has to house a piece whilst it's being sprayed Quote Link to comment Share on other sites More sharing options...
Tpt life Posted March 19, 2014 Report Share Posted March 19, 2014 Marco, you have a valid theory. The problem is that large pieces like cabinets will struggle to clear your enclosure. I worked in a lab with straight sulfuric acids with fumes that would eat your skin. The hood was all that was required but our projects fit completely inside the hood. Go for this if you want and only have the occasional large piece that you can spray elsewhere. 1 Quote Link to comment Share on other sites More sharing options...
AceHoleInOne Posted March 19, 2014 Report Share Posted March 19, 2014 Usually The problem with air not moving fast enough is the particles of finish in the air have time to stick to the wet surface resulting in a rough finish, in most of the open face booths your spraying close to the filter where the air is being drawn in so the particles are gone before they have time to dry, that's why I suggest spraying under an easy to build hood and then move the piece.... And all this isn't even taking into account any volatile fumes you might be spraying into the air !!( I know this isn't the case with Franklin but you never know what tomorrow brings )... I'm not sure how much air is pumped out of a spray gun but if I'm pumping out 100cfm of a harmful and possibly volatile gas I want to get rid of it just as fast specially in a closed booth. And please I'm by no means a professional on this stuff I'm just trying to remember things from a previous life Any finish particles that are floating in the air and land on a wet surface get incorporated back into a the finish. Its a dry finish that gets wet overspray sticking to it from to much air flow even off the gun (dry spray). Say your spraying a bunch of pieces and your spray booth is pulling wet finish that is coming off the gun over pieces that a curing. You will get a sandy surface. -Ace- Quote Link to comment Share on other sites More sharing options...
AceHoleInOne Posted March 19, 2014 Report Share Posted March 19, 2014 If I had a spray booth in my living room moving the right amount of air I would have no problem with it. My shop is detached. So this is your garage workshop you spray in? -Ace- Quote Link to comment Share on other sites More sharing options...
AceHoleInOne Posted March 19, 2014 Report Share Posted March 19, 2014 Thanks for all the replies guys, it seems maybe my original idea is not so good. What if I reduce the size of my spray area, like was suggested above? Would that allow the furnace fan to expel enough air to make it safe? I don't want to be risk my health of my family for my hobby. Woodworking is dangerous proposition. Listen to PB, have a professionally installed spray booth and call it done. -Ace- Quote Link to comment Share on other sites More sharing options...
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