Thread: Air purifier using a box fan

They work OK when there's not much fine dust around but as soon as they become partially clogged the air flow drops pretty dramatically so a sensitive differential pressure gauge is really needed to detect this and then either clean or replace the filters. Thats why its better/easier to vent or remove dust at source by other means.

This post went missing for a while so I posted again. Now it shows up! Now it's gone.

Originally Posted by mwells

... Has anyone done measures with this type of arrangement? Does the radial fan have enough static pressure to pull air to through the filters? Does it clean the air appreciably?

Mark

Yes, yes and yes.

I've done a lot of testing on a single filter version but not the setup you're asking about. For that, I've worked with others testing the four filter arrangement, providing guidance and analysis but, frustratingly, not hands on.

That testing was done with a Dylos 1100 Pro in a 13,000 (est.) cubic foot shop with sanding dust. For particles between 0.5 and 2.5 micron the time constant was 19 Minutes. This indicates a clean air equivalent ventilation rate of about 680 CFM.

I don't know what the ventilation recommendations are for schools but if you have a formula then 680 CFM would be a good guesstimate to plug in for box fan / filter combo.

Yes, yes and yes.I've done a lot of testing on a single filter version but not the setup you're asking about. For that, I've worked with others testing the four filter arrangement, providing guidance and analysis but, frustratingly, not hands on.

dmorse, if you're kinda an expert in this sphere of business, or so, what do you think about the complete home air quality test within such system like 5 stage whole Home Portable Air Purification System ? I've read a lot of positive recommendations all over the web. Especially talking of the ratio of price and quality. Do you think is it worth it?

Originally Posted by morrgan51

dmorse, if you're kinda an expert in this sphere of business, or so, what do you think about the complete home air quality test within such system like 5 stage whole Home Portable Air Purification System ? I've read a lot of positive recommendations all over the web. Especially talking of the ratio of price and quality. Do you think is it worth it?

Because anyone can call any sort of filter a HEPA filter I wouldn't buy anything the doesn't specify a Particle filtration size/efficient rating.

The 5 stage system says it uses a 99.97% efficient @ 0.3microns which is very good but it also only delivers up to 250 CFM up which means the flow rate will decrease as the filters clog up.
For say a 2500 sqm house with 2.4m ceilings that's 6000 cuft so you are getting about one room air change every 24 minutes or 2.5 air changes per hour. However, unless an air purification system is ducted, in practice it does work out that evenly. The air in the room that the purifier is located in will be purified much more often that say a room furthest away from the purifier.
If you have an open plan home then putting that purifier in the main open should provide good filtration.

The thing to remember is these filters will not filter out CO2 so while there's a temptation to seal your house up like a drum to get all the air purified, it can be counter proactive as this builds up CO2 levels which are not good for you. You may wish to invest in a budget CO2 meter to monitor this if you decide to seal your house up. Letting more fresh air on of course will being in more dust.

With 4 filters to maintain you should probably find out the expected life time and cost of each filter. If your house has any carpets or pets expect the filters to clog up quickly. In fact before you get the filter I would ditch the carpets - they are one of the greatest contributors to dust inside a house.

Unless you have a specific allergy I wouldn't bother with replacing the 2 chemical filters - just more this to clog up and slow the air down.

Originally Posted by morrgan51

dmorse, if you're kinda an expert in this sphere of business, or so, what do you think about the complete home air quality test within such system like 5 stage whole Home Portable Air Purification System ? I've read a lot of positive recommendations all over the web. Especially talking of the ratio of price and quality. Do you think is it worth it?

It's a bit of an exaggeration to call that a "whole house" unit. In the US the Industry standard for air cleaners is AHAM AC-1. If the CADR (clean air delivery rate) were actually "Powerful European motor delivers up to 250 CFM of purified air" 250 CFM that unit would be rated for 388 square feet. Ok if you live in a RV I guess.

A MERV 12 in the HVAC would do a better job in an average house.

Edit: Sorry, I was focused on dust. The MERV 12 would do better with dust and smoke control. It would not do anything for VOCs and has no germicidal UV nor PCO capability, but the 250 CFM is still a bit low to justify the "whole house" claim.

I built one of these for my workshop and decommissioned weeks later in favor of forced ventilation. The filters work, however, even in my small shop, they clogged up very quickly. The thing is a big box. If you have the space to spare, it is good and cheap to run one. Inside a house, they will be great.