Bad Air Day?

justK · #1 2006-11-06, 3:44pm

I wonder if anybody else ever has this problem. I have a strong vent fan with a hood over my workspace, I've done the 'incense' test, and really the fan is strong enough to create a vacuum in the room that will pull the door shut, so I have confidence that it is adequate for my work. I have two outside doors open for cross-ventilation. However, sometimes I still get a bit of irritation when I work--kind of a sore throat.
It happened today, it's very rainy and humid; I wonder if that could have anything to do with it...I often get uptight when I feel it and have re-run every test I can think of. The fan's pull is quite strong...It's entirely possible that dust in the studio could be getting kicked up and causing it...I seem to be allergic to everything.

I'm interested to hear what the vent gurus have to say!
Thanks,
Kim

Dale M. · #2 2006-11-06, 4:43pm

Its really hard to say.... Have you tried working with a respirator to eliminate the "bad air" theory....

3M - N100 ( or P100 ) or equivalent is probably the best you can use for this type of work. The cost $7-9 (I believe) at most home improvement or hardware stores. It may be worth a try...

Dale

MikeAurelius · #3 2006-11-07, 6:22am

Kim - it's possible that your fan is too strong and you are picking up outside irritants, such as pollen or dust. Do you have any allergies? Do your eyes get red and itchy?

I'd try Dale's suggestion of a N100 mask. If that works, it will then point to an environmental factor.

It does concern me that you comment that the fan is strong enough to pull a door shut - this is a very strong indication that you are using way too much fan for your application.

justK · #4 2006-11-07, 7:28am

Thanks guys,
The fan won't pull the door closed on its own so much as it 'helps' when I'm doing it. Kind of like when there's a window open in the house?
I bet I have some of those masks around, will try one. I am definitely suseptible to airborne irritants.
I believe my fan is a 600cfm, 3x2 hood, it's just above the ceiling vented out the roof.
While we're talking fans, do y'alll have any suggestions for how to muffle the sound? It is as loud as a hothead! I can't decide whether I should try insulating between the fan and the attic floor, or wrapping something around the ductwork, or both. Also no idea what to use...acoustic foam is so expensive!
Kim

MikeAurelius · #5 2006-11-08, 5:28am

There are two types of sounds - air movement and fan sounds. The first thing to do is to determine if you have vibration noise or actual motor noise. There's not much you can do about motor noise, but vibration noise can be cut down to almost nothing by being sure that all the ducts are braced, that there is no movement of metal against metal.

It will take some sleuthing work and liberal applications of metallic duct tape, but the time is well spent if it removes the source of the noise.

justK · #6 2006-11-09, 5:49am

Thanks Mike, I'm pretty sure It's just vibration sound. My dad will be delighted to pitch in anytime duct tape is involved...I bet I can get him to donate some acoustic foam too...
By the way, I've been using the Aura Shield for some months now and it's terrific! --except that I get nose prints on it from trying to see my teeny beads, LOL.
Kim

MikeAurelius · #7 2006-11-09, 6:28am

LOL - just tell him to use the metallic tape instead of the classic vinyl tape. If you use the metallic tape, you won't have to replace it in 2-3 years.

justK · #8 2006-11-25, 1:59pm

Update:
Today I finally did some work on the duct to try and dampen the noise. I stuffed some insulation into the gap between the ceiling and attic floor, and wrapped the duct work with batting. I used both kinds of duct tape

.

I think it has helped some. It's definitely just the noise of the fan. If I'd known it would be so loud--of course the duct and hood work like a trumpet to amplify the noise--I would have specified that the builders place it further up, closer to the roof...probably an easy enough project, will try it soon.
Thanks for the tips, that foil duct tape is cool stuff!
Kim

IF-Designs · #9 2006-11-25, 2:08pm

if its raining could the strong rain be obstructing the exit flow of your exhaust and then lowering your CFM's? Could this be possible Dale ? Mike any ideas? Ive been thinking about this and wondering with severe winds, rain and snows in my area I wonder sometimes if this can affect the ventilation I have. Unless you have something in your ventilation to keep backpressure from happening I think this could possible happen.

Dale M. · #10 2006-11-25, 4:11pm

If one has shutters or vanes on end of vent duct yes its possible wind pressure could be holding them closes.... But with usual gustiness of wind, I would bet one could sense the change in flow through work area... Having a vertical exhaust stack and having it above ridge line of roof and proper vent cap usually guarantees that wind will not be a problem.

Dale

MikeAurelius · #11 2006-11-25, 6:03pm

Wind blowing into a shutter or vane, as Dale mentions, will have an effect on them. Keep in mind that we are dealing with air velocities in the range of 2000 to 2500 feet per minute. Wind velocity and hence pressure is much higher than that and can easily overcome not only a shutter or vane, but an open duct as well.

A 10 MPH wind has an air velocity of around 3 MILLION feet per minute.