How to Trim Expensive Metal Humidifier Blankets

We moved and had to have the whole house humidifier replaced...I was used to the typical Aprilaire brand, but this one was different. I asked the furnace guy what size to get, and ordered them from online thinking I'd get a better price. They were a GREAT price....unfortunately, they were also 2" too long! These things are very lightweight and delicate - like a giant metal sponge or huge piece of toast. I looked all over the internet and couldn't find ANYONE who had ever trimmed one. So I guess I may be the first! It was worth the risk since the correct sized filters were a LOT more expensive than these - (like almost twice the cost!) so I was going to give it a try. I knew that if I used a saw it would tear the delicate aluminum webbing apart and a blade would crush it. Then I remembered the electric knife I had in storage from my gluten free bread baking days! Since it cost me all of about $6 at a thrift store, and I've seen many of them at garage sales, I thought I would sacrifice my knife to a possible great use. It worked! It worked so well, that you could even cut the sides of a pad as well - went straight through like...wait for it.....cutting bread! I hope this saves someone else the money it's going to save me. My furnace guy thinks I'm either a genius or nuts. (but he did feel bad for telling me the wrong size to get....) Enjoy~!

1. Filter (or blanket or pad whatever you want to call it)

2. Electric knife

3. Tape or lightweight rubberband or string

4. Box to cut on.

My filter (Or pad or blanket) was 2” too long. It was also a pinch too wide, but I was able to slide it into the frame, so I really didn’t want to trim the side. The MOST IMPORTANT thing to know is which is the top. NEVER TRIM THE TOP!!!! These things have a gravity flow to them and that’s why they go to the trouble of marking the top of them so you will install them right side up and not have water running everywhere because they’re upside down. I tried using a sharpie to mark it, but the coating on them is a clay substance and they’re also very bumpy. I settled on a piece of tape, but even that didn’t stick well. I would imagine that a lightweight rubber band would work well too. Just not so strong that it crushes the filter. As the tape slipped off while cutting I just eye-balled the rest of the 2".

Grab your electric knife and find someplace to cut. I turned my filter on its side and just cut downward. It didn’t take much pressure and sliced right straight through like bread! Notice there’s no crushing or ripping of the filter. Since the knife has 2 blades that saw opposite each other the cutting is very clean. Now install your filter!