Trapping Smoke/Particulates

[sjwaste]

I think I've seen these in bars, but I'm not sure. They look like large AC units, but they sit directly above and suck in the smoky air.

Do these vent to the outside, or do they clean the air and recirculate? I'm mostly interested in the latter, and how one accomplishes that. What materials and processes are used to do it?

Any ideas? Google didn't give me much in the way of technical details. Would running the air through activated charcoal work, or do you need to condense it all out? I don't know why, but I just got curious about how these things work.

 

[Rubycon]

They are HEPA - High Efficiency Particle Arresting filters designed to trap particles under a micron in size. This effectively removes the smoke particles from the surrounding air. To adsorb odors the air is passed through a post filter consisting of granular activated carbon or GAC.

 

[spikespiegal]

Uh-no, smoke eaters used in commercial installations tend to be electrostatic (I used to clean them). HEPA involves filters that typically have to be replaced, so they aren't a good option for high air flow areas because you'll be spending a fortune replacing the filters.

Electrostatic filters typically involve cleaning a grill and replacing it.

Electrostatic filters have fallen in popularity over the the past decade because of their reputated reputation as ozone makers. However, I'm seeing a slight increase in their recent popularity because passive units are low power, efficient and quiet. Problem is they can't move a lot of air because of ozone issues.

In short, a HEPA certified unit will work, but you'll spend more money the more efficient the filters are.

 

[Rubycon]

A properly DESIGNED and MAINTAINED electrostatic or electronic air cleaner will NOT produce corona generated ozone. Few in commercial establishments were maintained correctly hence their decline in popularity.

HEPA requires a powerful fan design and works well as long as the GAC elements are exchanged regularly.

 

[sjwaste]

Interesting. I used to have a small air cleaner that used both a HEPA filter and an ionizer. I never tried it with smoke, but I might need to light a cigarette in front of it and see what happens. I don't actually smoke, so I'd have to go get some, but I'll report back with the results

To my knowledge, the unit doesn't have a GAC filter, so basically the air coming out won't be smoky but will still stink, right? Or does an electrostatic element also remove the odor?

 

[Rubycon]

Vapors and fumes are adsorbed in GAC. Electrostatic precipitators can designed to remove a plethora of particulates, however.

Ionizer is a tricky term as many devices simply pass a stream of air between wires with a dielectric that's biased with a high enough voltage to produce a corona. This will generate ozone and is not considered healthy to have in a room with people.

Ozone has its uses for elimination of organic smells but in many non professional applications its use is often misapplied.

 

[spikespiegal]

A properly DESIGNED and MAINTAINED electrostatic or electronic air cleaner will NOT produce corona generated ozone.

Not disagreeing, but the industry fact is the reason you see far more HEPA / mechanical based air filters with powerful fans -vs- electro statics is for this reason - ozone. Once the EPA started yelping about it of course. The only home electrostatic units you tend to see have very little air flow because of ozone fears.

HEPA requires a powerful fan design and works well as long as the GAC elements are exchanged regularly.

Not disagreeing either....just not into the noise they make and constantly changing those expensive cartridges.

I'd really like to see more effort put into electrostatic because because like you said the ozone issue can be resolved with proper design. Also, HEPA pundits can rant all they want, but from a physics standpoint an electrostatic has the potential to pull out far smaller particles than GAC.

What I've never understood is why you need to produce an initial ion corona in the first place. It would seem that having a collection plate or grid that had a substantial differential in ionic charge than the surrounding crud in the air would accomplish the same thing, and not have an issue with ozone / O3. Just look at all the crud that builds up in your computer for instance.