I just posted this in the Saftey area, but someone here might want to see it to.
I am not totally happy with my new ventilation system, but it appears to work fairly well and satisfies most of my requirements even though I had to make more compromises than I am happy with. It is WAY better than our old setup.
Our previous temporary setup was not good. We would open the garage door and move the table out about two feet. We then had a fan blowing new air from the door on the other side of the shop. This is a picture of it:
Here is a quick view of the new setup:
When designing the new setup, I had these requirements:
1) Acceptable ventilation for standard tasks.
2) Adequate space for two people to work at the same time.
3) Ability to work standing or seated.
4) Minimal structural changes to house.
5) Ability to do advanced techniques like fuming possible.
6) Fitting into current garage workshop.
7) Maintain reasonable cost ceiling.
Reasonably quick to build so that it would get done!
I wanted to have a box enclosure to maximize fume capture. I decided to make the back out of cement board and the sides and top out of steel flashing. I debated this with myself a lot and wandered around between designs that were all cement board and all metal.
I originally planned on making it 8'x3' but when I was at my parents getting their pickup to haul materials, I saw an old metal table frame up by one of the barns. The plywood top was rotted out, but since I was going to use cement board, that wasn't a problem. It was 3' wide, but only measured 7'4" long. I decided a ready made metal frame was a good start and would help on requirement 8 above so I made a compromise on the length.
I made another compromise on the exhaust fan. I would have preferred a squirrel cage fan, but didn't find any locally. I went with a 1540cfm gable mount attic exhaust from Home Depot. I may need to replace this in the future, but it seems to work very well currently. It is mounted in the wall directly behind the enclosure and connected with three inches of flashing making a super short vent run/extension to the existing walls of the fan.
The standard open area of the front is 84 inches long by 20 inches high for 11.67 square feet. The 1540 cfm fan should be more than enough to to handle most tasks.
I did smoke tests with multiple paper towel rolls in different torch positions and the smoke was drawn away straight to the fan very quickly. I am thinking about adding some curved flashing in the top of the enclosure to further help funnel the fumes towards the fan and not give them any right angles to collide and mix around in just in case.
To make it possible for me to do some work standing, I made a two foot wide cutout in the front of the enclosure right in front of the exhaust fan. This will have most of the fumes going straight out the fan, but there is still a seven inch overhang to catch and fumes. I have made a cover with flashing that fits over the inside of the existing cutout area that can be latched in place when two people are working seated.
I put flashing over the cement board. This gives a nice work surface that can be easily cleaned. The inside of the hood is exactly seven feet, which gives each person three feet by three feet of space and leaves a one foot DMZ in the middle. I noticed that Angelique is already lining her new mandrel blocks I made her up along the edge to make a fence.
The hood is lighted with four 150 watt halogens giving 600 watts of power to make it easy to see even with boro glasses on.
This is the bench after it's first night of use. The flashlight is there so I could see to shut off the tanks and wind the hoses back up. I need to get a better light out back.
This was a fairly cheap setup to make and hopefully will be up to the job for a while. It ran about $300 in materials. A singe person setup would have been MUCH easier and cheaper to design and build though.
Cheers,
Better vents and more space!
