Air purifier

Hi !
In my darkroom construction, I thought a device to filter the air was a good idea.
I came accros a device which is a filter (3 kind : charcoal, bacterial, and another one called HEPA ???) is also adv. as a device to kill germs, and gives away a negative ionization. This last part puzzle me, as I wonder if it is harmless to photgraphic films and papers ?
What do you think about this ?

The charcoal will absorb many odors.

Can't recall off hand what HEPA actually stands for, but it indicates the finest filtration possible. Virtually no particulates, no matter how tiny, get through.

The negative ions won't hurt anything. They are a product of running the air past electrically-charged grids which attract the particles.

Sounds like a nifty unit which will dramatically reduce your darkroom dust problems.

There has been much tv advertising locally about the superiority of one type of filter over another. My personal experience has been that even the really cheap models make a significant difference in the amount of dust floating around to get on negatives and in holders.

I tried a filter with ions, it generates ozone which in the confined area gave me headaches so I got rid of it. I now just have a mechanical filter that seems to work ok..

Air and water filters are the best thing for clean prints. Keep the room closed at all times and run the air filter when developing film, not loading it in the tank. Turn off for drying the film.

I think I forgot how to spot it has been so long.

Keeping door shut requires little operation of the air filter

I use two Hunter small ones, one in the enlarging room and one in the wet room. They are HEPA. An electronic one from Sharper Image will do as well.

GeorgesGiralt said:

Hi !
In my darkroom construction, I thought a device to filter the air was a good idea.

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The best solution for the darkroom, in my opinion, is a Venta Air Cleaner: http://www.venta-luftwaescher.de/ or http://www.venta-airwasher.com/ (English)
It does not throw dust around, gets the air humidity to a level to reduce static etc.
They work well and are quite popular among many of the artisan labs here. I use ours in the winter to improve the living spaces and inbetween (and when out of the heating season) in my darkroom.

Vertical trays like the Nova print processors too help to keep the air climate nice.

GeorgesGiralt said:

Hi !
I and gives away a negative ionization. This last part puzzle me, as I wonder if it is harmless to photgraphic films and papers ?

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If you have a lot of problems with static discharge then get a Simco ESD fan. They tend to be not too expensive on the surplus market--- and are great for working on electronics. I have one to work on computer boards but use it as well to prepare my negative packaging line (moving film from the dryer into "endless" sleeves) .

The ozone generating machines clean the air but remember that ozone is a powerful oxidizer. Maybe the quantity is too low, I don't know, but ozone is the stuff that prematurely ages prints and negs. Your filters or air exchange with the outside are probably the best.

Ozone is bad for you, too, not just for your prints -- in extremely small quantities, it's invigorating, and a component of the "thunderstorm" smell. In not much more concentration, it will burn your lungs, throat, nose, and eyes, and even at the lower concentrations long term exposure is a known carcinogen.

HEPA stands for "Home Environmental Protection Agency", which is a standard setting body for air filtration. A HEPA filter is required to remove some very high percentage of particulates down to some very small size, and to process a set volume of air through a specified area of filter material without clogging or losing effectiveness. If you have an electrostatic, carbon, and HEPA filter, you should get air out that would be clean enough to suit any application except spacecraft assembly and microchip fabrication (both of which require a higher particulate removal standard).

For a darkroom, a HEPA filter by itself is most likely plenty; if you have fume or odor buildup, you need fresh air ventilation, not a better filter.

Donald Qualls said:

Ozone is bad for you, too, not just for your prints -- in extremely small quantities, it's invigorating, and a component of the "thunderstorm" smell. In not much more concentration, it will burn your lungs, throat, nose, and eyes, and even at the lower concentrations long term exposure is a known carcinogen.

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For a darkroom, a HEPA filter by itself is most likely plenty; if you have fume or odor buildup, you need fresh air ventilation, not a better filter.

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Hi !
Thanks for your input ! But, In France where I live, one has choice between a very pricey unit without the ozone generation (giving out ozone) and the one I look at (which gives "negative ions for your health and safety" So now my question is : How to get rid of the ozone ?

As for air change, I am set up ! I've a 250 cubic meter per hour shuffling filtered air (the real rate is something about 210 cubic meters taken the filter loss into account) and an exhaust fan of 160 cubic meters per hour. The intake it near the dry side and enlarger, and extraction takes place on the wall of the sink where all nasty chemicals will be.
But as the room is part of the basement, dust is an issue. So I plan to put the cheap air filter. Any idea to destroy ozone will be appreciated !
Thanks !

Well, the ozone generating array is electric, so it might be possible for you to just disconnect it. It will most likely be a metal looking grid with wires banded across it. Find it's powersource and disconnect it.. at your own risk of course!

A correctly made ion generator shouldn't produce ozone. I don't know of any ozone generators sold in this country; they may be illegal because of the health hazards of concentrating ozone and long term exposure. Ozone is one of the components of photochemical smog that have led to such things as California regulating sale of all VOCs (volatile organic chemicals), because atmospheric breakdown of these chemicals by sunlight generates ozone.

Ions are not the same as ozone, in any case, but an ion generator does nothing to protect your prints, either.

However, I might point out that with the level of airflow you're talking about, a recirculating filter in the room will be moot, completely overwhelmed by dust introduced through your intake; you're talking about completely changing the air in your darkroom several times an hour, right?. Much better to spend the same money upgrading the intake filter. Having higher flow on intake than on exhaust is good; it will pressurize the room and any air leaks will be outward (taking dust with them) rather than inward (bringing dust in).

You may not be able to get a HEPA filter as such in France; it's an American government standard, but you want your intake filter to be a great deal better than the usual central heating duct filter (which seem designed mainly to catch the dead flies that get sucked into the cold air return; they're too coarse to catch dust at all).

Disconnecting the "ozone generating" array in the air filter will likely disable the whole filter, or greatly reduce its efficiency, anyway; the ozone is probably a side effect of an electrostatic filter which works by using a high voltage to spray a charge onto particles in the incoming air stream, and then cause those particles to deposit onto plates (which, BTW, require periodic cleaning). In the US, you can see filters like this with the brand "Smokeeter" in bars and taverns; I have one (with the Sears Roebuck brand on it) in my living room that I'm trying to find a way to get into my darkroom when it's set up. Mine, at least, generates no detectable level of ozone most of the time (using the Mk. 1 Schnozz detector system) -- the only time I smell anything from it is when it arcs.

Donald Qualls said:

A correctly made ion generator shouldn't produce ozone. I don't know of any ozone generators sold in this country; they may be illegal because of the health hazards of concentrating ozone and long term exposure. Ozone is one of the components of photochemical smog that have led to such things as California regulating sale of all VOCs (volatile organic chemicals), because atmospheric breakdown of these chemicals by sunlight generates ozone.

Ions are not the same as ozone, in any case, but an ion generator does nothing to protect your prints, either.

However, I might point out that with the level of airflow you're talking about, a recirculating filter in the room will be moot, completely overwhelmed by dust introduced through your intake; you're talking about completely changing the air in your darkroom several times an hour, right?. Much better to spend the same money upgrading the intake filter. Having higher flow on intake than on exhaust is good; it will pressurize the room and any air leaks will be outward (taking dust with them) rather than inward (bringing dust in).

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Well if I calculate well, as my room is pretty air tight, air flow will be near the exhaust fan rating, so 160 cubic m per hour. (a little higher than the exhaust rating, because pressure will be a pinch above the normal pressure)
My intake is already filtered by a special filter ( air cond style) which was sold to me as to be _really_ effective. It should be due to the price I paid for it.....
As the darkroom is in a basement, it will be naturally dark, quite light tight, and with as few air leaks as I think is possible. As it is quite separated from the house, I fear that the air will stay steady for long period, and collect dust from the leaks. So I thought a good idea to make the air go through a high quality filter killing germs and purifying the whole...
As my wife suffer from allergia, if it proves unsuccefull in the darkroom I givi it to her ;-)

HEPA stands for "High Efficiency Particulate Air" (filter). A google search finds connections between HEPA filters and ISO Standard 14644 for clean rooms, but it is not clear to me whether consumer-grade devices pay any attention to that standard.