Thread: Room Air Filters - ??

Don't have the same brand as that one, but they're generally very quiet, no need for hearing protection.

In terms of filtration the two Room air filters I have measured were not as effective at filtering the very fine dust as either a needle felt bag or a pleated filter.

Rather than using a room air fliter I recommend improving your dust collection at the source and vent the DC outside if you can.
How are you using your DC while you are turning? Do you know about "Bell shaped mouth" dust collection ports?
If not have a look here.

Originally Posted by Phily

I have a standard 6m x 6m shed with a 2hp ducted extractor connected to my numerous machines. All good, though I am not capturing all the dust - especially when sanding on the lathe. I'm therefore thinking of adding a room air filter unit

The best approach to really ANY dust collection problem is to improve collection at the source and have it captured or vented outside as efficiently as possible.

If you have the biggest dusty you can afford or have the available power to run, the most effective ducting and collection ports in use at the machine and have maximized filtering or venting outside to eliminate the fine dust, then you need to look at other options if the problem persists.

As BobL points out, room filters will not remove the fine particles as well as common DC filters. If you are venting back into the shed and your filters are efficient to X microns and your room filter is efficient to Y microns, if Y is larger than X, then the filters are really not going to pick up anything that the dust collection lets through. But it might pick up some of the particles that the dust collection system misses.

Another way to do it is to use bathroom style exhaust fans. I have a plywood board that slips into the window in my shed and holds two standard bathroom exhaust fans, venting outside. I can run these independently or together and the rated airflow was calculated to change over the shed pretty quickly. It was a while back but I worked it out that if I run them for half an hour after finishing dustmaking activities it should do what it needs to do. The same board allows my 2hp dusty to vent directly outside.

This is far cheaper than room filters as a capital expense and also as a running cost, particularly when looking at filter costs as well as electricity.

Room filters were designed to allow people to heat their workshop and have the already warm, filtered air returned to the shop as it is filtered. I can see no costing model that would suggest that room filters are the way to go unless you are in a very cold climate for a long time every year. Otherwise, use the biggest dusty that can run within the restrictions you have, have the best collection ports on your machines that you can have and increase airflow through your workspace as much as you can to remove the fine dust BEFORE it settles

In my own case, room filters are not a practical or economic solution to any problem I have.

Doug

Originally Posted by doug3030

Room filters were designed to allow people to heat their workshop and have the already warm, filtered air returned to the shop as it is filtered. I can see no costing model that would suggest that room filters are the way to go unless you are in a very cold climate for a long time every year.

In terms of overall dust control I agree with Doug - its far better to tackle it at source rather than trying to herd the stuff after it has escaped into the shed.

However, although they weren't specifically designed for the opposite application (ie very hot climates) they are worth considering if you have air-conditioning (like me) and don't want to run your externally vented DC for some time after the last dust making activity since this continues to remove cooled air from a workshop.

In terms of the efficiency of commercially available room air filters, it's not like they are useless - they will (eventually) scrub the air of wood dust in the shed. However, their lower efficiency means it takes them longer to filter the air than a 2HP or bigger DC would do it so overall fine wood dust exposure to any operator will usually be greater than using a vented DC. The reason for this is that they are both slower and less efficient that most >2HP DCs (an externally vented DC is theoretically 100% efficient at fine dust filtration) ). I have calculated the comparative time room air filters will take to clear a shed of fine wood dust compared to a large externally vented DC and from memory it was between 2 and 10 times longer.

If you don't run your externally vented DC for some time after your last dust making activity, or use a VC with auto switching power tools, or have limited ventilation then they are better than nothing.

Where room air filters do beat any externally vented DC is for finishing, and the reason is as follows.
A vented DC will drag external air into a shed and depending where you live and the length of your grandmothers nose this air will contain dust that may spoil a finish. Since room air filters don't vent they can reduce the overall dust load inside a shed well below that possible by using a vented DC. If you are after quality finishes then a room air filter also has some merit.

FWIW, my room air filter is an ultraclean laboratory unit rated at HEPA U15 (99.9995% efficient at 0.3 microns or greater) - it's an 800 CFM unit and it only consumes 120W of power so much cheaper to run electrickery wise than a DC. However, I only run it in the manner described above. ie hot day, aircon on, make the dust with the DC on and then switch DC off and run the filter. Ideally I should use this all the time since it is effectively as efficient as external venting but I don't want to clog up the filter too quickly as they are not cleanable and a new filter costs ~$700! I am fortunate to have several spare filters that I got for nothing as they were contaminated by a tiny amount of smoke but they were still going to be thrown away. The Unit is not exactly whisper quite but I sometimes forget it's running until I come back to the shed the following day - the air in the shed is then very clean - of course me opening the door immediately contaminates it.

Hi Phily

I run a 2hp dusty with a 1 micron filter and 2 Jet AFS-1000B air filter systems with Wynn after market filters fitted. The Jets are run from the time I enter the shed till an hour after & leave it. I have 2 spiders that live in the shed and it has been a long time since I have seen dust on their webs.

Jet Filters

At the same time I also work hard at collecting as much of the dust at the source that I can, as Bob will tell you it's an on going battle.

Ross

Originally Posted by Ross

. . . . I have 2 spiders that live in the shed and it has been a long time since I have seen dust on their webs.

Only 2

The "Spider web dust detector", I like it although some spiders will keep their webs clean.

Originally Posted by BobL

Only 2

Yeah I leave 2 as dust detectors.

The "Spider web dust detector", I like it although some spiders will keep their webs clean.

They dismanle their webs and spin new ones.


Ross

This is great advice guys. One of the problems I have is that a few of my older (Luna) machines while brilliant heavy old units, were built before the idea of dust collection was in vogue. Short of installing a 300hp extraction unit there is no escaping the fact that dust extraction at the source will be inefficient. I have installed a "big mouth" extraction unit similar to the Bell unit described, though its not that effective (I suspect that long lengths of corrugated piping are reducing the effective suction power). The bathroom fan units are a great idea - did you manufacturer hoods to weatherproof them ?

As for the weather questions: I live in a cool and wet climate (Southern Highlands of NSW) but am not too stressed on the temperature front. Being an expert producer of well shaped firewood blocks I have plenty of fuel for my slow combustion heater !!

The other consideration is noise pollution. My 2hp dusty is quite loud and I'm concerned that the neighbours may loose patience if I install another noisy unit - hence the thought of the internal unit. I'm now leaning toward a re-work of my ducting and source collection together with a few well placed extraction fans.

Originally Posted by Phily

This is great advice guys. One of the problems I have is that a few of my older (Luna) machines while brilliant heavy old units, were built before the idea of dust collection was in vogue. Short of installing a 300hp extraction unit there is no escaping the fact that dust extraction at the source will be inefficient. I have installed a "big mouth" extraction unit similar to the Bell unit described, though its not that effective.

The Big mouth is almost a complete opposite in its air draw characteristics to a bell mouth. The Big mouth draws air more or less evenly into itself over the full width of the angle of the mouth and more and also provides a significant back resistance to air flow so it actually reduces the amount of air sucked in by the DC, and the air draw pattern means that air speed rapidly diminishes with distance. In contrast a bell mouth has a near zero resistance and more importantly draws more air from directly in front of the opening so the drop off with distance is about half that of other openings. This enables much better dust collection at sources. It does of course assume that the bell mouth is pointed at the dust source and that the dust source has a width of no more than the width of the mouth.

(I suspect that long lengths of corrugated piping are reducing the effective suction power).

How long are the lengths and is it 4" in Diam?
Using 4" (solid or flexy) on any DC of 2HP or larger is the number one choke point for dust collection.
2HP DCs can pull 1000+ CFM but use 4" ducting of any length will reduce the flow to <400 CFM. Corrugated pipe any longer than one metre will produce a further Reduction

The other consideration is noise pollution. My 2hp dusty is quite loud and I'm concerned that the neighbours may loose patience if I install another noisy unit - hence the thought of the internal unit. I'm now leaning toward a re-work of my ducting and source collection together with a few well placed extraction fans.

I live on 1/8th of an acre about 1 mile from city centre but my DC is still outside but in a sound reducing enclosure. It works a treat and is no louder that the neighbours pool pump at the fence line.

I always thought the main reason for putting DCs outside was that the filters still let too much fine dust through but my measurements in more than 15 woodworkers sheds indicates that this is not the case. The biggest problem is dust leaks. Virtually all DCs leak - most are bleedingly obvious but short of using a particle detector every time you turn it on there is often no way of finding them all so it's just better to put or vent DCs outside.

Thanbks Bob, bordering on embarrasing you have confirmed my suspicions re my set up. I have used 4" corrugated ducting from the external dusty throughought my shed and it would be at least 10m of pipe from the extractor to the lathe. When sanding I can literally watch the dust float up and away from the big mouth; clearly the corrugated pipe has a serious impact on flow compounded by the dissipation of flow at the collection point as you describe.

One of the reasons I went with the flexi pipe was simply because I couldn't find any adapters from 4 or 6 inch pvc pipes to the 4 inch vent pipes; after trolling several stores and numerous catalogues I decided to make do with just the flexi pipe.

I suspect also that the dusty is louder than it would normally be due to the increased workload caused by the long lengths of corrugated pipe. I have lined the external cupboard with 2" polystyrene and carpet and mounted the unit on foam blocks but it still shrieks at uncomfortable levels.

looks like I have to do more research on duct pipes and replace the existing set up as the priority over investing in backup units.

One advantage of mys setup however is a distinct lack of spiders - I suspect that they have become too frustrated over the continual cleaning and rebuilding of theiir webs due to all the dust !

Cheers

Originally Posted by Phily

Thanbks Bob, bordering on embarrasing you have confirmed my suspicions re my set up. I have used 4" corrugated ducting from the external dusty throughought my shed and it would be at least 10m of pipe from the extractor to the lathe.

Oh dear - mind you that is not the first time I have heard/seen this sort of thing.

6" to 4" sewage pipe adapters ( called level inverts) are very common in plumbing store. YOu can also get these on-line.

Philly,

All of the below sounds like good advice to me.

I installed 6" PVC pipe for dust collection, and that helps a lot compared to 4". However, upgrading machine ports from 4" to 6" and making machine hoods/shrouds that keep the airflow high and get it moving in the right direction also made a big difference. Surprisingly (for me) making the hoods/shrouds, whilst a bit fiddly in places, was not difficult.

If you are interested, more details on hoods/shrouds is here ... https://www.woodworkforums.com/f200/m...66/index6.html

Looks like it will be definitely worth the effort of working on the hoods. Frustrating re the advice on the adaptors though - I originally visited Bunnings and Home Hardware with this in mind but neither seemed to stock the adapters which is the primary reason for going with the flex. Looks like an excuse for another visit !!

Philly,

Had the same problem with the adaptors. You likely need to visit a specialist plumbing supply outlet or Carbatec, who sell a metal version for $10.00 each.

Got mine from Carbatec, because plumbing outlets charge like wounded buffalo. If you have a Total Eden store nearby, they are worth a look. In my area they are about 40% cheaper than the plumbing suppliers. My Total Eden store will have any out-of-stock item in store the next day.