Our basement at work is a bit mouldy/stale, there is an extractor in there but i'd like to clean the air additionally with an air filter.
Problem is we work in there and it gets a bit dusty so i'm guessing a hepa type unit would be costly in filters. And I read that the filterless types are largely ineffective.
So I'm either looking for something with large, reasonably priced filters or a filterless one that is up to the job.
When I was diagnosed asthmatic and dust-sensitive, some ten years ago, in a fit of overkill we went out and bought a Bionaire BAP625 (that particular model is probably no longer available). Can't remember what we paid for it though. It has two levels of dust filtration; coarse and fine (HEPA). The coarse filters (two, side by side) are simply sheets of that black expanded foam stuff that most computer cooling fans have, and that's also used for packaging integrated circuits to eliminate static charge. The two fine filters are like multi-folded thick paper. So far it's been run almost continuously for ten years without any problems whatsoever. Every couple of months 'er indoors opens it up to carefully vacuum the dust from the filters. The instruction book said that the fine filters would eventually become clogged and need replacing, but not so far. There's a string of indicator lights that are supposed to show pressure building up across the fine filters as they clog, but ours has never moved off the lowest light. We live in the country, so perhaps just not a lot of fine dust about, or perhaps they're just for show. 'Er indoors also reckons it significantly reduces the amount of dusting she has to do. Well, that's her story!
have a Bionaire/Holmes BAP242 which has been used almost continuously for nearly 4 years now without any problems,I don't replace the HEPA filter, I just vacuum it gently which seems to do the job. The coarse pre-filter doesn't fit very well but I believe the above website mentions a modification:
" You can lower filter costs by replacing the too-small factory prefilter with a piece of 3/8 inch thick urethane foam"
What does H&S say about it? I'd be more inclined to seal the walls and floors etc to prevent the formation of dust rather than try and sort it afterwards. Unless the dust is produced by machinery - in which case it should be extracted at that point.
If it is mouldy/stale, I would hazard a guess that there is no fresh air supply (or it doesn't work), no openable windows and some sort of extract that draws air in through any cracks in the structure, under doors, etc..
If there are people working in there regularly (not a store room) they need a supply of fresh air from outside and this needs an AHU with panel & bag filters and a heater. The building may have an air supply system already. Forget the Bionaire stuff, it's domestic and won't cope. If it hasn't got a fresh air supply already, it probably isn't meant to be a habitable room and you'd need to verify the fire alarm and means of escape allow it to be occupied.
Air filter units which sit in the room are quite ineffective. They capture only a small proportion of airborne particles and do next to nothing for smells. Although many claim to filter the air several times an hour in fact what they do is filter some of the air several times an hour. There is nothing to direct air through them so it is often the same air going around and most of it going nowhere near them. Also note all the ratings for these units are at full speed, they make so much noise most are only ever run at minimum speed and the length of time the filters last without needing cleaning or replacing is testimony to their ineffectiveness.
Typically the absolute minimum number of air changes per hour for an occupied room should be 4. The air purifier will have only a very small proportion of this air pass through it so any slight effect will be due to ionisers fitted to some. Note however that any ioniser (be it a stand alone unit of part of a filter unit) will produce ozone in small quantities but often sufficient to induce bronchospasm in people with asthma. Ozone also increases sensitivity to mould so an ioniser may not be at all suitable for your specific location.
There are probably three types of that black plastic foam...
Plain coloured foam.
The conductive stuff used for integrated circuits - don't know if that's ever used for filters.
Non-conducting electrostatically charged foam designed to attract and trap dust much smaller than the hole sizes in it would otherwise trap.
When I worked for a minicomputer manufacturer over 20 years ago, we bought giant rolls of the 3rd type which we made into filters to fit in the front of our rack units. Whilst being manufactured, it's exposed to extremely high voltage potential, and that locks a static charge into it for life (even survives washing with water and washing- up liquid). This charge tends to attract small particles, which stick in the filter, without using a fine filter which would generate significant air resistance which would impede the system cooling.
I had several sheets of it when I left (we melted it onto stiff wire frames for slotting into the racks), but after about 15 years (whether used or not), it crumbles to pieces.
I have no idea what it's called or where you could find it nowadays, although google turns up hits for washable electrostatic foam filters which are probably the same stuff.
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