Thread: Room Air Cleaner

Would like to also know if anyone has upgraded the filter cartridges, e.g. to trap smaller particles.

Originally Posted by emotiv

Hi All,

Am considering on purchasing an Air Cleaner for the shed/workshop.

Deciding between:
https://www.timbecon.com.au/sherwood...ner-air-filter
Carbatec Room Air Filter - 1/6HP with 5 Micron Filter | Carbatec

The Carbatec unit states:
Effectively filters 98% of 5 micron (and 85% of 1 micron) particles

Does this mean 15% of 1 micron particles hitting the filter will not be trapped or does it mean that mean in a room cleaning scenario it should get 85% or the dust in the room. Other particles have either settled or cannot be reached by the filter, in which case you may just need better circulation.

Settling is not considered.
The Standard test for a Room Air Filter (RAF) is
A) what is the concentration of dust of a given particle size in the air going into the filter
AND
B what is the concentration of a given particle size dust in the air coming out the filter.
The value of B/A*100 is used to determine the stated values,

Provided no other dust is generated, How often the same shed air passes through the RAF determines the ultimate cleanliness of the air.

EG
if your shed is say 20 x 20 x 8ft this 3200cuft, AT 400 CFM that means in theory it takes 8 minutes for a sheds worth of air to pass through the RAF or ~8 room air changes per hour.
After 1 room air changes, theoretically 85% is filtered so after 2 room air changes or 8 minutes
0.85 + (1-0.85) =97.5
After 3 room air changes its 99.965%
After 4 room ar changes its 99.99%

In practice (even in a shed with circulation) some of the air that has already passed thru the RAF passes through it again before some unfiltered air gets filtered.
Experiments show (even in a shed with circulation) it takes about 2X longer to filter all the air so allow 16 minutes for one shed air filtration cycle, or 4 room air changes per hour.

RAF use very low power fans so replacing the filters with filters capable of of finer filtration will almost certainly reduce the air flow - the same eventually happens with the RAFs above. Filters get blocked and they get slower and slower to the point of being ineffective. It my not seems like the filters are blocked but without careful measurement you cannot tell what the flow is.

A zero maintenance alternative is simple forced ventilation (exhaust fans in teh walls or windows of teh shed).
This replaces dusty shed air with cleaner external air.
The process requires more air movement - target air flow is 10 -20 room air changes per hour.
There are no filters so small fans can be quite effective.

What sort of DC have you got and does it vent outside the shed. Just venting teh DC outside teh shed may remove the need for a RAF.

ThanksBobL.

That makes sense and like how you included the calculations and example.

I was considering the alternative you mentioned by installing some "bathroom" like inline exhaust fans at opposite ends to cycle the air will have to look at the CFM for such fans. Was attracted to the out of the box solution

Was also considering putting one of these in on the longest wall but was unsure of the noise level these things generated, anyone know the db levels or done the same?
DETROIT Ventilation Fan & 5m Hose DPV30 | Total Tools

Regarding the current DC I have a 2 stage cyclone unit with a pleated filter, it is currently in the shed but my plan is to build a box for it outside and duct the hoses in for space and to not introduce any particles back in the filter has missed.

My shed is 2.4W x 5.2L x 2.2 H (with a pitched roof).

Originally Posted by emotiv

Was also considering putting one of these in on the longest wall but was unsure of the noise level these things generated, anyone know the db levels or done the same?
DETROIT Ventilation Fan & 5m Hose DPV30 | Total Tools

Beware, those things (like all axial fans) are pretty noisy.

Look for the fans bought by the "grow your own" community - they have an interest in VERY quiet , high air movement

Regarding the current DC I have a 2 stage cyclone unit with a pleated filter, it is currently in the shed but my plan is to build a box for it outside and duct the hoses in for space and to not introduce any particles back in the filter has missed.

Try venting outside first and see if this fixes it.

Originally Posted by BobL

Beware, those things (like all axial fans) are pretty noisy.

Look for the fans bought by the "grow your own" community - they have an interest in VERY quiet , high air movement

Try venting outside first and see if this fixes it.

hey bob, not to hijack the thread, but is there any real theory about fan placement for this?

i have a fairly generic 6 x 7 x 2.8 double garage (120m3) with a window in the back, but wondering if i'm better with 2x 580m3 (claimed) exhaust fans. or aim for one 1100m3 fan for roughly the same price as the two.

wasn't sure if encouraging the air out over two areas would be better then just one central location

I've wondered this also and based on reading it is better to have two smaller ones esp. if you have odd shaped room. I would think it is better from a circulation point of view.

Regarding how high and where I found this useful: Air filtration in your workshop | IGM Tools & Machinery