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Ventilation of New Darkroom Question
I'm just completing the drywall on a new darkroom about 16'X10' with a 8'
ceiling ~1300 cubic feet. How much ventilation do I need? How do I calc. CFMs/air exchange. How big a pipe do I need. I'm doing B&W, Color and maybe Cibachrome work. The room is in a basement and I was thinking of tying into an existing bathroom fan pipe (4" I'm guessing). Would I need to put a backflow type of value to protect the bathroom? As I mentioned the bathroom is adjacent to the darkroom. I've debated putting a vent in the wall between the two rooms and keeping both doors closed and turning on the bathroom fan while working too drawing the stale air into the bathroom and then out. Is this advisable? (It is after all a basement bathroom) Thx. for any help with this. |
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Ventilation of New Darkroom Question
"SofaKing" wrote in message news:qoLWb.469845$JQ1.90903@pd7tw1no... Common sense tells me if you just attach to the existing vent pipe, the post fan air flow will take the path of least resistance. That means if the fan is at the top of the stack, it would be OK to attach the darkroom to the same pipe. If the fan is built into the vent in the bathroom, you may end up blowing all your fumes in there, unless you put a backflow flapper in there. If I recall correctly, the recommendation is 10 complete air changes per hour. So you would need to move 13,000 CF per hours or 216 CFM. Most of the manufacturers of darkroom ventilation products are using 6" ducting. Hope this has been helpful. Jim __________________________________________________ _____________________________ Posted Via Uncensored-News.Com - Accounts Starting At $6.95 - http://www.uncensored-news.com The Worlds Uncensored News Source |
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Ventilation of New Darkroom Question
"SofaKing" wrote in
news:qoLWb.469845$JQ1.90903@pd7tw1no: [...] guessing). Would I need to put a backflow type of value to protect the bathroom? As I mentioned the bathroom is adjacent to the darkroom. I've debated putting a vent in the wall between the two rooms and keeping both doors closed and turning on the bathroom fan while working too drawing the stale air into the bathroom and then out. Is this advisable? (It is after all a basement bathroom) Thx. for any help with this. When we put new fan in our bathroom (the kind where the fan is at the ceilng), it had a backflow flapper thing where the duct attaches to the fan. The one that was removed had one too. So you might already have one. I would not put a vent into the bathroom except as a last resort, and if I did it at all, I would make sure I could seal it off when it wasn't in use. Bob |
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Ventilation of New Darkroom Question
Sofa* -- ASME (American Association of Mechanical Engineers) recommendation is
10 to 20 air changes per hour and I like 15 to 20 air changes per hour - in part for removal of heat and moisture/humidity. And with 1300 cu.ft. something around 350 CFM would do a good job for you. Now, I recommend that you pressurize your darkroom - i.e. blow air into the darkroom instead of sucking air out of it. The reason - it keeps the dust and dirt out of the darkroom. The typical bathroom fan is a blade type fan. Consider using a squirrel cage blower - a much more positive movement of air. In my case - I mounted a blower high on an outside wall of the darkroom - in an unfinished part of the basement. The air flows down the wall between the wall studs and exits near floor level. The exhaust vent is positioned high above the sink. Another comment regarding the flapper check valves - is good. --- Jerry/Idaho |
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Ventilation of New Darkroom Question
On Thu, 12 Feb 2004 13:41:42 GMT, "SofaKing"
wrote: I'm just completing the drywall on a new darkroom A few ideas concerning fans: Fans are often rated for "free air" airflow, which is much greater than the actual installed airflow due to resistance in filters, ducts, and vents. Use a fan with a "free air" CFM rating at least 50% greater than your calculated required airflow. Large slow fans are generally quieter than small fast fans. Many fans are rated in "sones". The lower the sones value, the quieter the fan. To minimize dust, pressurize the room and filter the supply air. I built a frame to hold a "high performance" furnace filter over the fan intake. This provides a filter area much larger than the fan input to minimize resistance to airflow. A timer switch for the fan will make it convenient to run the fan for several hours after a darkroom session to dry out the room. Locate the supply vent high on a wall to avoid blowing dust up from the floor, and as far from the sink as possible to avoid blowing chemical vapors around the room. Locate the exhaust vent near the sink below nose level to draw chemical vapors away from your face. In new construction, the cavity between wall studs can make a good light trap. Locate one vent high and the other low, and paint the interior of the stud cavity flat black. Be sure the supply air cavity is clean (and filter the supply vent just to be sure.) Chris Ellinger Ann Arbor, MI some zone plate photos: http://www.ellingerphoto.com/ |
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Ventilation of New Darkroom Question
Yes it's giving me a better picture. Thanks.
"Jim Phelps" wrote in message ... "SofaKing" wrote in message news:qoLWb.469845$JQ1.90903@pd7tw1no... Common sense tells me if you just attach to the existing vent pipe, the post fan air flow will take the path of least resistance. That means if the fan is at the top of the stack, it would be OK to attach the darkroom to the same pipe. If the fan is built into the vent in the bathroom, you may end up blowing all your fumes in there, unless you put a backflow flapper in there. If I recall correctly, the recommendation is 10 complete air changes per hour. So you would need to move 13,000 CF per hours or 216 CFM. Most of the manufacturers of darkroom ventilation products are using 6" ducting. Hope this has been helpful. Jim __________________________________________________ __________________________ ___ Posted Via Uncensored-News.Com - Accounts Starting At $6.95 - http://www.uncensored-news.com The Worlds Uncensored News Source |
#7
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Ventilation of New Darkroom Question
Is that recommendation for darkrooms or houses in general? Most off the
shelf bathroom fans seem to be just over 100 CFMs. I'm thinking I'll have to move up to something heavier to achieve 10-15 air changes. The blower you describe it blows the air into your darkroom and it enters the room at ground level? "Jtown2354" wrote in message ... Sofa* -- ASME (American Association of Mechanical Engineers) recommendation is 10 to 20 air changes per hour and I like 15 to 20 air changes per hour - in part for removal of heat and moisture/humidity. And with 1300 cu.ft. something around 350 CFM would do a good job for you. Now, I recommend that you pressurize your darkroom - i.e. blow air into the darkroom instead of sucking air out of it. The reason - it keeps the dust and dirt out of the darkroom. The typical bathroom fan is a blade type fan. Consider using a squirrel cage blower - a much more positive movement of air. In my case - I mounted a blower high on an outside wall of the darkroom - in an unfinished part of the basement. The air flows down the wall between the wall studs and exits near floor level. The exhaust vent is positioned high above the sink. Another comment regarding the flapper check valves - is good. --- Jerry/Idaho |
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Ventilation of New Darkroom Question
Thank you that's a good idea about not blowing the air around the room. I'm
thinking I'll use three HVAC vents from Home Deport as the intake manifold above the sink and joing them to a 4" or 6" pipe which exhausts outside. At This point I could easily mount a fan to supply pressuse to the room under the sink or opposite the sink. "Chris Ellinger" wrote in message ... On Thu, 12 Feb 2004 13:41:42 GMT, "SofaKing" wrote: I'm just completing the drywall on a new darkroom A few ideas concerning fans: Fans are often rated for "free air" airflow, which is much greater than the actual installed airflow due to resistance in filters, ducts, and vents. Use a fan with a "free air" CFM rating at least 50% greater than your calculated required airflow. Large slow fans are generally quieter than small fast fans. Many fans are rated in "sones". The lower the sones value, the quieter the fan. To minimize dust, pressurize the room and filter the supply air. I built a frame to hold a "high performance" furnace filter over the fan intake. This provides a filter area much larger than the fan input to minimize resistance to airflow. A timer switch for the fan will make it convenient to run the fan for several hours after a darkroom session to dry out the room. Locate the supply vent high on a wall to avoid blowing dust up from the floor, and as far from the sink as possible to avoid blowing chemical vapors around the room. Locate the exhaust vent near the sink below nose level to draw chemical vapors away from your face. In new construction, the cavity between wall studs can make a good light trap. Locate one vent high and the other low, and paint the interior of the stud cavity flat black. Be sure the supply air cavity is clean (and filter the supply vent just to be sure.) Chris Ellinger Ann Arbor, MI some zone plate photos: http://www.ellingerphoto.com/ |
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Ventilation of New Darkroom Question
I'll agree with all the suggestions here. Placing a "range hood" over a sink
can still result in the user being in the path of fumes moving from the sink to the hood. I have seen designs which incorporate a length of perforated pipe along the back of the sink attached to the vent flue which draws fumes back away from the sink user. Positive pressure (pumping air into rather than out of) should result in a cleaner darkroom. Use a furnace filter over the air intake to the fan to prevent the ingestion of dust, and install some kind of backflow prevention flapper on the bathroom fan stack to prevent fumes being exhausted into the bathroom. I have used the partition lighttrap idea too, and it works fine for me. The bigger the ductwork, the better for airflow. Of course, if some really ugly incident takes place in the bathroom, the darkroom user could be in big trouble from bathroom fume backflow too.... "Chris Ellinger" wrote in message ... On Thu, 12 Feb 2004 13:41:42 GMT, "SofaKing" wrote: I'm just completing the drywall on a new darkroom A few ideas concerning fans: Fans are often rated for "free air" airflow, which is much greater than the actual installed airflow due to resistance in filters, ducts, and vents. Use a fan with a "free air" CFM rating at least 50% greater than your calculated required airflow. Large slow fans are generally quieter than small fast fans. Many fans are rated in "sones". The lower the sones value, the quieter the fan. To minimize dust, pressurize the room and filter the supply air. I built a frame to hold a "high performance" furnace filter over the fan intake. This provides a filter area much larger than the fan input to minimize resistance to airflow. A timer switch for the fan will make it convenient to run the fan for several hours after a darkroom session to dry out the room. Locate the supply vent high on a wall to avoid blowing dust up from the floor, and as far from the sink as possible to avoid blowing chemical vapors around the room. Locate the exhaust vent near the sink below nose level to draw chemical vapors away from your face. In new construction, the cavity between wall studs can make a good light trap. Locate one vent high and the other low, and paint the interior of the stud cavity flat black. Be sure the supply air cavity is clean (and filter the supply vent just to be sure.) Chris Ellinger Ann Arbor, MI some zone plate photos: http://www.ellingerphoto.com/ |
#10
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Ventilation of New Darkroom Question
"SofaKing" wrote in
news:qoLWb.469845$JQ1.90903@pd7tw1no: I'm just completing the drywall on a new darkroom about 16'X10' with a 8' ceiling ~1300 cubic feet. How much ventilation do I need? How do I calc. CFMs/air exchange. How big a pipe do I need. I'm doing B&W, Color and maybe Cibachrome work. The room is in a basement and I was thinking of tying into an existing bathroom fan pipe (4" I'm guessing). Would I need to put a backflow type of value to protect the bathroom? As I mentioned the bathroom is adjacent to the darkroom. I've debated putting a vent in the wall between the two rooms and keeping both doors closed and turning on the bathroom fan while working too drawing the stale air into the bathroom and then out. Is this advisable? (It is after all a basement bathroom) Thx. for any help with this. I would not vent into the bathroom. Some processes (especially toning) release some pretty oderiferous gases - the domestic heat you would get for dumping that into the bathroom would be miserable! Here's my suggestion. First, plan on a system that provides positive pressure in the darkroom. That means that the fan pushes air into the darkroom from which it vents outward by natural flow. The reason for this is that if the static air pressure in the darkroom is slightly higher than outside, the flow of air through parasitic vents (around receptacles, doors, etc) would take dust out of the darkroom rather than in. Second, plan to filter the air flow to minimize the inflow of dust through the ventillation system. For obvious reasons. What I did in my basement darkroom was to construct a box between a couple of ceiling joists outside the darkroom. I mounted a fan in one end of this box, and put a frame around the box so that I could slip an ordinary furnace air filter in to filter the air flowing into the box. The fan blows out of the box. Then, I used a flexible duct to connect the outlet of the fan to a vent inside the darkroom. The exhaust from the darkroom is via a large "cold air return" louvered vent mounted directly over the sink. I actually used a bathroom duct kit from Lowes that included both a length of flexible duct and a louvered flange that was intended for mounting outside the house when the duct is used to vent a bathroom. The reason I did this outside the darkroom was to minimize the distracting noise of the fan inside the darkroom. In my case, I used a computer-style muffin fan that was quiet to begin with - and in this arrangement, I can't hear it at all in the darkroom. I wired it to the master switch in the darkroom so that the fan is on whenever anything is being done in the darkroom and so it goes off when I leave the darkroom and turn off that master switch. The fan I bought is rated 60cfm. I suspect that with the duct, the actual flow is somewhat less. My darkroom is about 800 ft3 - which results in a very comfortable working condition. |
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