Air Filter Replacement

Not sure if the cabin air filer is HEPA or not but it is the same size as several other Toyota models. Some people have cut regular filter media to size using the original as a pattern.

 

Here is the MicronAir site referenced by Tideland, They cross reference a couple of other filters also that your father may be able to order.

http://www.micronair.us/Toyota/105

 

John's document is incorrect- the filter is absolutely *NOT* a HEPA filter.. In fact, no cabin filters for *any* make of vehicle are HEPA.. The small size of the filter, the high air flow requirements and the extremely variable air quality (especially since vehicle interior ventilation systems don't normally have a pre-filter) make a true HEPA filter unsuitable for the application.. They may be labeled as "High efficiency" or "High efficiency particulate" (I've just finished some equipment filtration specifications at work and common HVAC industry use of these terms means a filtration of 90% or better at a certain particle size (typically 2 microns), which is a typical "good" filter for most HVAC applications), but that does *not* make them HEPA (guaranteed 99.97% at 0.3 micron)- that last "A" in the acronym makes a huge difference in the actual filtration level!! Filter manufacturers will claim all sorts of efficiency numbers and acronyms, but they are all very careful not to claim "HEPA" when they are not, as they must be *certified* to bear the HEPA label.

A true HEPA filter of the small size in the Prius would clog up in just a few days of typical outdoor city air, and would introduce a significant amount of flow restriction even when brand-new and clean.. Other signs that this is NOT a HEPA filter include the fact that there are no polymer seals around the filter element or the filter tray- the seals are a requirement for true HEPA rating as just the small amount of air making it around filter at the edges would cause it to fail to meet HEPA filtration requirements; additionally, if you hold the OEM element up to the light, there are visible paths through to the other side- they're small to be sure, but on a true HEPA filter, the media is much thicker and the holes are so small that you can never directly see the light source..

The filter is simply a miniature high-efficiency filter of similar material to the better grade of household furnace filters.. I estimate that the filter is the equivalent of somewhere in the range of ASHRAE MERV 8-10.. I tried a piece of the high-end 3M Filtrete MERV 14 filter in my Prius and the restriction caused by the filter was much too high- the ventilation system sounded like a vacuum with a plugged hose (yet another reason why the OEM filter cannot possibly be a HEPA- if a MERV 14, which is very good, but still a lower filtration than HEPA is restrictive enough that it won't work in the car, there's no way that a true HEPA, with an even higher restriction level, would).. I went down to a MERV 10-11 filter with an activate charcoal layer to reduce odors which sounds close to the OEM filter when new but you can definitely hear the fans start to labor when the filter starts to get clogged, which supports my estimate of an equivalent MERV 8-10 rating on the OEM filter..

 

C4, do you have any comments on the passive electrostatic filters you can cut-to-size to fit the cabin filter carrier? They have a fairly high flow rate, but claim to catch small particles due to electrostatic attraction.

 

I changed mine early and was very surprised at how dirty it was. I am going to change mine at least every 10k and check it every 5k. I am going to look into cheaper alternatives to the OEM filter.

 

call 1-800-565-9743 "part #9927tc I believe" the guys name is Gary It is a parts shop in Canada. the guy is nice and the filters are the same as Toyota's and they are 9 to 10 dollars. I always buy two at a time. Of course that was before Prius number two, I guess it will be 4 now!!!

 

The "electrostatic" filters have very low restriction/high flow rate, but that's about their only advantage.. They do a pretty reasonable job at capturing larger particles but only a mediocre job filtering smaller particles, and then only when the filter is clean- as soon as the filter starts to load up and the filaments are covered up with dust, it "loses its charge" and the small particle filtration rate drops dramatically; like any other filter, the particle filtration improves somewhat as the filter loads, but because of the large open area in type of filter, the improvement is not significant.. No matter what their packaging and advertising claims, typical washable electrostatic filters only achieve a maximum equivalent of about a MERV 4 rating in real service, and again, that's only when clean.

If you're going to wash and clean the filter ever few weeks, it will probably do a reasonable enough job for a vehicle A/C system, but if air quality is your concern, you're much better off getting one of the cheap disposable pleated-media filters that are anywhere in the range of MERV 6-10 in the largest size you can, taking the filter out of its cardboard holder and just cutting out a square to replace every few months (note the higher the efficiency the filter, the more often you will have to replace it)... With the size of filter I buy, I can cut 8 Prius-sized filters with an activated charcoal layer; the filter lasts about 2-3 months (the charcoal actually gives out way before that and starts letting odors through, but it doesn't affect the particulate filtration)- in other words, I buy a large filter once every two years.. If you're really into pinching the pennies and live in an area with good outdoor air quality and don't have allergies, you may elect to go with a lower-efficiency filter, not only will it be cheaper, but it will go much longer between changes..