Negative pressure chemical storage cabinet

[doughpat]

Hi all -

First time posting, plenty of lurking in my past!

I'm building a new garage now, and thinking about ways to improve air quality in the garage. My "chemicals shelf" is an embarassment to my former chemistry-teacher self.....all kinds of stuff just sitting there. Pesticides, solvents, adhesives, paints, etc.

Once a jug or something gets opened, a residue inevitably remains on the container. Seals aren't perfect, spills, etc.

I'm thinking about retrofitting a cabinet to be "roughly" airtight, (just some foam/rubber gaskets on the doors and sealing up most of the holes). Then I'll take some kind of pump/blower/fan and rig it up so that it continuously ***** air through it and exhausts it through the exterior wall behind it, direct to outside.

This would need to be a very small amount of air, otherwise I'll be bringing a lot of cold air into the garage (though I suppose I could do a "direct vent" style setup where I actually supply exterior air to the cabinet as well -- but thats starting to defeat my "KISS" principals).

I almost wonder if a relatively large diaphragm air pump (aquarium air pump style) would do the job. If the cabinet were pretty well sealed, I bet it would (though hard to measure/assess).

Other options would be a very small squirrel-cage type blower.

I suppose it would make sense to figure out the fan/blower first, then just match the ducting/tubing according to that.

Any thoughts? Anyone done something like this?

I realize this wouldn't even remotely pass any kind of certification or professional standards, but I sure do like the idea of my 'nasties cabinet' being kept under a little bit of constant low-pressure.

 

[Sevenhills1952]

Computers have what we called boxer fans, about 5" square. They're quiet and can move a fair amount of air (All different cfm ranges). I put one in the house in a closet that was musty...it shoots air out into the crawl space vented outdoors.
If I was building a new garage I sure would think about how to add a small room, 6ft x 6ft probably plenty unless you want a parts washer. With shelves, easy to get to from garage, but a place for gas cans, paints, chemicals, etc. Fireproof, concrete floor, maybe cinder block, steel door.

Sent from my SM-S320VL using Tapatalk

 

[rlitman]

I use a 100mm computer fan to exhaust the closet where my cats deposit their waste. It works fantastically with an opening roughly 12" by 10" high.

It sounds like you've got experience working with a chemical vent hood. So you should know that their flow requirements are based on linear air velocity, which boils down to if you have good seals, you don't need much air flow.

But I'd suggest you just purchase a used flammables cabinet. These already have hookups for outside ventilation, and don't actually require active air flow.

 

[doughpat]

Yeah I wish I had the luxury of space for a whole ventilated room, but not this time!

Are you thinking something like these?
https://www.amazon.com/dp/B07W92ZCXM/?tag=atomicindus08-20

I think the problem with these types of "muffin fans" is that they perform very poorly once ducted and any amount of static pressure is added (i.e. ducting, bends, flappers, etc.). I think something with lower CFM but higher static pressure rating would be better.

I'm thinking something more like this:

Only thing is it'd take some Macgyvering to get it to attach to ducting. Would be nice if I could find something that would easily/air-tightly seal to some kind of semi-rigid pipe/duct.

I don't know much about this sort of thing but I think that a diaphragm pump is too high pressure (too low CFM, plus they're quite loud), a computer-style fan is the opposite (too high cfm, but too low pressure), and that a small squirrel-cage fan is a good compromise (decent pressure, decent CFM).

Just need to find the right fan and ducting...

This one would be cool, but probably more flow than I need. But I like the flange -- would probably be easy enough to rig that up to some flexible 1" conduit or something.

 

[LS6 Tommy]

I wouldn't use any type of fan or blower that isn't explosion proof for venting a chem cabinet. Probably cheaper in the long run to get a used flammables/chemical storage cabinet.

Tommy

 

[doughpat]

I use a 100mm computer fan to exhaust the closet where my cats deposit their waste. It works fantastically with an opening roughly 12" by 10" high.

It sounds like you've got experience working with a chemical vent hood. So you should know that their flow requirements are based on linear air velocity, which boils down to if you have good seals, you don't need much air flow.

But I'd suggest you just purchase a used flammables cabinet. These already have hookups for outside ventilation, and don't actually require active air flow.

Can you provide detailson how you've hooked up your computer fan to an exterior wall? What kind of ducting did you use? Any sense of the airflow?

I looked into flammables cabinets....lots of $/cubic foot, and most of them actually don't vent (intentionally). They are more about containing a fire that starts within them, so the idea is to seal them off completely. This would mean the vapors would build up internally until you open the doors, when they would vent into the room.....no bueno.

 

[doughpat]

I wouldn't use any type of fan or blower that isn't explosion proof for venting a chem cabinet. Probably cheaper in the long run to get a used flammables/chemical storage cabinet.

Tommy

I respectfully disagree. This is a situation with very low concentrations of "everyday" chemicals that hundreds of millions of people have just sitting around. Theres no need for specialized equipment here. The whole idea is to keep the concentration down with continuous airflow...

 

[rlitman]

I wouldn't use any type of fan or blower that isn't explosion proof for venting a chem cabinet. Probably cheaper in the long run to get a used flammables/chemical storage cabinet.

Tommy

Good point. Though technically a DC brushless fan should be explosion proof.

I respectfully disagree. This is a situation with very low concentrations of "everyday" chemicals that hundreds of millions of people have just sitting around. Theres no need for specialized equipment here. The whole idea is to keep the concentration down with continuous airflow...

Um, no! Millions of people store this stuff safely, because they're not sealing it up in airtight cabinets. You are planning to do just that.

When (not if), your fan starts to fail (most good fan bearings are rated for around 8 years of continuous use), it will start to slow down before you notice. And then the vapor concentrations can rise, and well. So, did you plan a tachometer alarm into your setup to let you know when it's failing? Because, your system is "fracture critical" around your fan.

As I said above, go with a passive ventilation system.

 

[rlitman]

Can you provide detailson how you've hooked up your computer fan to an exterior wall? What kind of ducting did you use? Any sense of the airflow?

I looked into flammables cabinets....lots of $/cubic foot, and most of them actually don't vent (intentionally). They are more about containing a fire that starts within them, so the idea is to seal them off completely. This would mean the vapors would build up internally until you open the doors, when they would vent into the room.....no bueno.

I used a 3” bath fan vent cover with aluminum tube through the wall, and drywall screws through the fan to hold it flush to the wall. No, you cannot feel the airflow at the door opening, but it is sufficient to keep all odors out of the adjacent hallway. You know when the fan isn’t working (over the years, I’ve replaced it twice) by the smells escaping.

Used flammable cabinets can be found affordably. I have two. They will have vent fittings. You can leave them sealed, or plumb the vents to the outside.

 

[nmantas]

I'd be careful of adding a combustion source (brush arc when some fan motors start) to a contained area of flammable chemicals. You'd hate to try to make a situation safer and inadvertently burn the place down.

 

[timewarp]

I respectfully disagree. This is a situation with very low concentrations of "everyday" chemicals that hundreds of millions of people have just sitting around. Theres no need for specialized equipment here. The whole idea is to keep the concentration down with continuous airflow...

What happens when the power goes out for a couple days, the vapors concentrate because of no airflow, then the fan kicks on with a little spark because it's not explosion proof, then you get an explosion or fire?

 

[Firebrick43]

Why not just have a 2” pvc pipe vent through the roof? Run near the ridge and have the pipe stick up past the ridge it will draft. Seal the cabinet and place a bbq lid vent in the side and you can easily control the draft.

 

[Vintage Veloce]

This.

I wouldn't use any type of fan or blower that isn't explosion proof for venting a chem cabinet. Probably cheaper in the long run to get a used flammables/chemical storage cabinet.

Tommy