HEPA Filter adapter for 120mm Fan

This is an adapter/filter holder to fit an LV-H128 HEPA filter to a 120mm fan. It's primary purpose is to filter extracted air from an enclosure. 

The back of the filter body is designed to mount a 120mm fan. There are two body styles. One for heat-press inserts and M4 bolts. The second is for M4 bolts and hex nuts.

There are also two lid styles. One is an open design. The second has a place to mount a 120mm fan using M3/M4 nuts and bolts. Try to keep the inner fastener profiles as lean as possible. Although there's a bit of a gap between the filter and the lid, if your bolts are too long they'll impact the filter. The lids attach with M4 or M5 bolts, or whatever you've got that'll fit in the larger holes.

You can mount the filter with the airflow going in either direction as needed, by using either the fan mounting point on the back of the filter or the lid with a fan mount.

The LV-H128 is a pretty beefy filter, so your fan will need to have a good static pressure to move air through it. I find the most effective method is to pull air through rather than push, but if your fan is strong enough, either will work. My preferred fan setup (with Amazon links) is:

• Noctua NF-F12 iPPC 3000 PWM, Heavy Duty Cooling Fan - https://www.amazon.com/gp/product/B00KFCRATC 
• Noctua NA-FC1, 4-Pin PWM Fan Controller - https://www.amazon.com/gp/product/B072M2HKSN 
• Fan Power Adapter 12V 2A DC External Power Supply - https://www.amazon.com/gp/product/B071V9CQ5H (Or any similar)

The NF-F12 runs pretty quiet at mid-range speeds. At full power it's louder, but not terribly so. However, it's got power to spare.

The filters I'm using are “generic” filters. Any LV-H128 style filter should fit, but I'm using these: https://www.amazon.com/gp/product/B08PV559JP 

I also tend to use my fan covers, to make things just look a bit cleaner. You can find those here: https://www.printables.com/model/722956-120mm-fan-cover 

In the picture with the grey filter body with the purple-covered fan attached, I'm using 40mm M4 bolts with washers and hex nuts to hold the fan to the filter using the fan-mount lid. The filter body is using the heat-press inserts and is attached to the side panel of my enclosure. The fan is pulling air from the enclosure, through the filter, and exhausting it out. There's a second fan (using the same fan setup as above) on the other side of the enclosure using this filter holder https://www.printables.com/model/737138-120mm-fan-filter-holder to push clean, cooler air into the enclosure. I find this setup works great for keeping a constant 28c to about 31c environment in the enclosure. You can use the PWM controllers to increase or decrease that general temp a bit, but it really depends on your enclosure and how hot you're running your build plate.