Dear WeatherCat household maintainers,
Forced air furnaces are very common and many houses now have central air conditioning. These systems have one thing in common - a filter. For many years we have been using 3M filters under the trademark: Filtrete. Here is the manufacturer's product listing.
https://www.3m.com/3M/en_US/p/c/filtration-separation/filter-cartridges-media/air/i/consumer/The main selling point of this brand of filter is that they can trap extremely fine particles while not restricting the air flow too much. This photo of the wrapper lists some of the pollutants the MPR 2200 Filtrete model claims to remove:
Unfortunately that leaves the problem of determining when these filters are plugged and need replacing. I was regrettably lax in replacing our filters until our furnace blower motor failed. That involved a repair of over $1500!!
Not surprising, after that I put furnace replacement on a rigorous schedule, but even that wasn't ideal. In California we have perennial misery of smoke from wildfires. That smoke can plug a filter very quickly, so it was really desirable to have some way to determine when a filter was restricting the airflow.
For over a year now, 3M has been marketing a "smart" filter with a flow sensor that would communicate via Bluetooth. These filters are not surprisingly more expensive than their conventional counterparts. So to get customers "hooked," 3M provided a special offer to Costco members at prices actually below the retail prices of their conventional filters.
That was an offer I couldn't refuse, so I bought enough of their Filtrete MPR 2200 filters to last what had been our consumption for year. Here is a link to this particular product:
https://www.3m.com/3M/en_US/p/d/b00040220/I installed the first filter in the end of January and started to monitor. The big question was exactly how long would these filter continue to be usable?
3M has provided a free iOS (and Android) app for the purpose of monitoring your filter and doing all sorts of other things (more on that later.) Here is a link to the iOS app on the Apple app website:
https://apps.apple.com/us/app/filtrete-smart/id1340390225Nonetheless, by far the most important duty of this app is to allow you to monitor your filter. This is the first unfortunate limitation of this technology. Bluetooth is by design a short range protocol (at best around 30 feet or 10 meters.) Moreover, the designers of furnaces had no reason to consider radio transmission in the design of their steel cases. We replaced our furnace in 2009, so it is relatively modern. Nonetheless, the only positive way I've found to check the status of a filter is to bring my iPhone right up against the case of the furnace. Moreover, our furnace is located in a utility room next to the garage. I simply don't bring my iPhone next to the furnace very often. So the hope that Filtrete app will automatically connect to your filter simply isn't realistic. As a result, instead of having the app monitor your filter and only alert you when the filter needs changing, instead this app becomes a periodic nag to remind you to connect your phone to the filter so it can get a reading. It is a minor annoyance in the broad scheme of things, but definitely falls short of the hopes of many in terms of the automated household.
The following is a view of the main "pane" of the Filtrete iOS app:
I spliced together the top and bottom half since you cannot see all of this on a second generation iPhone SE. There are two points to note on this screen. The first is the dubious air quality information. While not completely wrong, I can get much more accurate data from the Purple Air website. This morning the data was way off. Here is the report from the 3M app:
Here is the report from Purple Air at the same time:
At best this is more of an annoying distraction than helpful. The bottom half illustrates the issue associated with the limitations of Bluetooth. Eventually, you'll get a notification asking you to manually connect to the filter.
Not surprisingly for a free app, it is "nosey" in ways I dislike. Here is the main preference screen:
There are two options which are greyed out, both having to do with sharing your location. As you can see both are locked to
yes. The explanation for this is to allow you to monitor more than one filter - GPS being the way to distinguish between filter locations. Okay, I can see owners of multiple properties wanting such a thing, but there is no way to turn location tracking if you are a simple home owner. Of course 3M promises not to use this information in unsavory ways, but if that was truly honest - let 3M prove it by allowing me to turn this off. There is a second screen that rubs me the wrong way called "My Home:"
As you can see, 3M simply comes out and claims this is purely for "recommendations" (of 3M products.) Beyond the obvious issues associated with pets and smokers, the remaining categories are a bit vague. Just what will 3M recommend if you check either "allergies" or "respiratory conditions?"
Other panes of this app allow you automatically order replacements (directly from 3M at of course 3M retail pricing.) If P.T. Barnum's quip about:
"there's a sucker born every minute" is true, 3M will definitely make money on this app.
At this point this review would seem to have nothing to offer but negativism - but don't give up hope just yet! The 64 dollar question remains unanswered: just how long will such filters last? At some level I must confess it is something of the candy advertising ploy: "How many licks does it take to get to the center of a tootsie pop?" Nonetheless even if I've been chicken to push these filters to the limit, I've been very impressed by their longevity. Making the required visits to the furnace, the 3M app reported that our first filter was still good at the end of May! It was that filter that I finally decided to change at the end of November. Here is the app report on that filter:
Note that the app conveniently notes the installation date so you don't have record it somewhere. It is time to dig into the details of the filter element itself. Here is a photo of the filter I removed:
This photo is taken of the "bottom" (the side receiving the air from the return ducts.) As you can see, it look rather dirty. I certainly wouldn't have expected that it still had over 1/2 of its life to use. You can discern a band at the center which I think is caused by a lower vacuum pressure from the blower. You can also see an oval slightly above center that will be revealing in the next picture:
This is the new filter that I installed. As you can see, not surprisingly, the filter elements start out as a pure white. Nonetheless it furthers the point of how difficult it is to judge by eye how dirty a filter actually is. The other point of interest is the circular object corresponding to the oval on the previous picture. Here is a close-up of what turns out to be flow meter and Bluetooth transmitter:
The paper tab prevent the battery from making contact until you are ready to use the filter. That prevents premature battery wear and insures that you won't accidentally pair with a filter that isn't yet in use.
Unfortunately, the transmitter flow meter is intended to be disposable and you must activate a new one with each filter. This seems wasteful and hardly earth friendly. I would have much preferred a two component design where a single permanent low meter and Bluetooth transmitter were mounted on one filter after another. That would have allowed for high-quality electronics to be used and would have avoided the repeated creation of
"e-waste" with the discarding of each filter. For bonus points, 3M could have designed the flow meter and Bluetooth transmitter with rechargeable batteries to avoid battery waste. Alas, I fear that many so-called "green consumers" would not want this logistical hassle even if that would be better for the environment. Ironically, the two-component design would actually be easier even on the consumer. 3M explicitly demands that all local laws with respect to "e-waste" be adhered to. That means when you replace a filter, you need pry off the old transmitter to include in our local e-waste collections. While 3M warns you to be careful in this removal because the wires reinforcing the filter are very sharp - I nonetheless managed to cut myself when replacing the filter in May. All-in-all, a 2-component product would have been a much better system, if only consumers were savvy enough to understand that.
Having gone though the process, I can provide one more screen capture to show what a newly installed filter looks like:
So what is my verdict? I definitely do not like the design of these smart filters or the iOS app, but they do what they claim to do - inform me condition of the filter element. I was plainly throwing filters away unnecessarily. Thanks to the built-in flow-meters, I can see these filters can be used for many months - instead of weeks!
I am aware of even better filter options. There are electrostatic filters that are even more efficient and can be cleaned instead of throwing the filter element away. Unfortunately, there wasn't enough space in our utility room to fit such a filter in the furnace intake plenum. Even our limited options, these 3M filters are serving us very well. So if you have considered these filters but were unsure, I would recommend that you at least give them a try. The cost of one filter isn't extreme and if it works as well for you as it has for us - I think you will be pleased!
Cheers, Edouard
![[cheers1]](https://athena.trixology.com/Smileys/default/food-smiley-004.gif "Cheers")
