Any Good (HEPA) Air Purifiers of Small Size & w/o Pre-Filters?

[kyphysics]

https://www.amazon.com/dp/B00007E7RY/?tag=pfamazon01-20

I've owned different versions of the above air purifier. It's big and clunky and uses a "pre-filter" that wraps around the internal HEPA filter core.

The HEPA filter is not changed regularly, but the pre-filter must be annoyingly changed every 3 months (that's what the manual recommends, but I've used a 4-6 month time scale for changing mine). At 6 months, I admit the pre-filter is nasty and has all sorts of white and grey matter stuck to it (I run the purifier about 10 hours a day - rotating rooms). The pre-filter filters out larger particles and those that make it past the pre-filter will meet their demise at the HEPA filter.

Negatives - you have to pay $35-45 for those pre-filters. That adds up to significant yearly money.

Does anyone use a HEPA filter (or better - True HEPA, etc.) air purifier that weighs less than 15 pounds and doesn't use pre-filters? I'd love to get a new model that I don't have to break my back to lug around and doesn't require constant ~$40 maintenance costs.

Tangentially-Related: Does any use a good HEPA vacuum (not a small handheld) that is less than $300. I find that the good ones cost $300+ mostly.

 

[Wrichik Basu]

Negatives - you have to pay $35-45 for those pre-filters. That adds up to significant yearly money.

Does anyone use a HEPA filter (or better - True HEPA, etc.) air purifier that weighs less than 15 pounds and doesn't use pre-filters?

In the absence of a pre-filter, you will have to change the HEPA filters periodically. Are pre-filters costlier than HEPA filters?

 

[kyphysics]

In the absence of a pre-filter, you will have to change the HEPA filters periodically. Are pre-filters costlier than HEPA filters?

I wish there was a design of one that didn't require those costs at all. . .at least not 3-4x a year.

 

[russ_watters]

There's a few principles that should be understood here:

• Since a HEPA filter eliminates basically all particles in its airstream, the exact efficiency of the filter isn't very important. The effectiveness of the device is almost entirely a function of airflow. Twice the airflow, twice the particles removed from the air (roughly). So, airflow is pretty much the only significant indicator of an air purifier's performance.
• Airflow is proportional to physical size/filter area. So bigger filters/units means better filtration.
• Filter efficiency is not a function of filter load, but airflow is. But it also takes a lot of filter loading to significantly affect airflow. Only change filters when they look heavily loaded. Also, consider cleaning them instead of changing them.

 

[jrmichler]

You can reduce the cost by adding an additional prefilter over the existing prefilter. Filter blanket material is available in most hardware stores, which is where I found this:

The pressure drop is very low, and it is cheap.

 

[FactChecker]

You can reduce the cost by adding an additional prefilter over the existing prefilter. Filter blanket material is available in most hardware stores, which is where I found this:
View attachment 333675
The pressure drop is very low, and it is cheap.

Great idea! But I am not sure that that looks like the advertised 1" thick. I would check that. ;-)

 

[kyphysics]

There's a few principles that should be understood here:

• Since a HEPA filter eliminates basically all particles in its airstream, the exact efficiency of the filter isn't very important. The effectiveness of the device is almost entirely a function of airflow. Twice the airflow, twice the particles removed from the air (roughly). So, airflow is pretty much the only significant indicator of an air purifier's performance.
• Airflow is proportional to physical size/filter area. So bigger filters/units means better filtration.
• Filter efficiency is not a function of filter load, but airflow is. But it also takes a lot of filter loading to significantly affect airflow. Only change filters when they look heavily loaded. Also, consider cleaning them instead of changing them.

Thanks for informative post.

Do you or anyone else have any thoughts on placement of a purifier. I don't mean so much in terms of room location laterally, but more so in terms of height. I try to place mine in the center of the room (occasionally I'll rotate closer to the edges to try capture more there, but it's mostly center), but I've always wondered about height. I started placing mine on the floor, but then thought about particles floating in the air higher above it. So, I'd alternative at times. I'd sometimes raise it up on a table. Obviously, I can't put this gargantuan purifier on a string to hang like a foot or two from ceiling, but would height matter in terms of the machine's ability to capture all the stuff floating in a room HIGHER than the placement?

 

[kyphysics]

You can reduce the cost by adding an additional prefilter over the existing prefilter. Filter blanket material is available in most hardware stores, which is where I found this:
View attachment 333675
The pressure drop is very low, and it is cheap.

Would that 3rd filter layer reduce the suctioning ability of the fan in the purifier (i.e., like giving it too many barriers?

 

[russ_watters]

Do you or anyone else have any thoughts on placement of a purifier. I don't mean so much in terms of room location laterally, but more so in terms of height.

Height shouldn't matter. Most air purifiers pull air in from the sides and exhaust out the top. This creates a circulation pattern which pushes particles down.....which is where they want to go anyway due to gravity.