According to lecture I went to, MERV 11 to 13 are good for smoke. I bought some random cheap filter. Next time I change it, should look into what filters my hvac system supports.
One big thing to remember is that as a filter is used, it starts to get dirty and that adds even more strain on your furnace fan/blower. So a MERV 13 filter in a month like this is going to be catching even more ash and needs to be changed more frequently to not over-strain your motor.
If you want to get into the numbers: a MERV 8 filter has about a 0.3” w.g. pressure drop (clean) vs a MERV 13 which has 0.4” pressure drop. Common maintenance procedure is to replace your filter when it’s dirty to the point that the pressure has doubled compared to the clean levels (0.6” and 0.8” respectively). From that assumption there’s likely a world where people have a dirty MERV 8 filter that’s running at 0.6” pressure drop and they could replace it with a clean MERV 13 and lower the load on the blower (for a short time until it becomes dirty)! If asked when that new MERV 13 would become too dirty, I couldnt say. Maybe a couple months under normal conditions, but with all this smoke it’s anyone’s guess.
looks like there was the option to get a panel that accepts a 2" filter, but that wasn’t selected. Something to think about if I’m doing anything to it in the future.
Seems like there’s a lot of evidence that 4" thick filters are better than 1". Can use a higher merv rating withiut causing as much restriction.
I’ve used 1900 filters in my current system and they work fine. Just change them before they get clogged. It’s true that it’s the lowest pressure drop 1” filter, lower than even other lower merv filters or even other 3M filtrete products. I had previously used $1 “washable” filters and my AC evaporator became absolutely caked with dust and started to smell (which is also a health concern). The 1900 stopped this because it filtered much better and the particles ended up on the filter and not the AC evaporator.
So little useful information from the manufacturers online. Everything’s a brand name, you don’t get any tables of CFM data to be able to make an informed decision on what you can get.
Went to cantire. Bestair merv 8 has essentially the same 0.19 initial pressure drop at 820 cfm as 3m 1900. 3m 1900 merv 13 is lower than merv 12 I had in before (0.22).
It kind of makes sense - merv is a measure of filtration quality, only indirectly correlated with the airflow. as filter tech gets better over time I would expect MERV to get better given the same
Amazing what a vacuum of quality info there is on the 'net about this though. It’s all AI SEO blogspam. If it wasn’t for reddit there’d be no deep knowledge at all.