How-To: Cleaning / Changing Laser Fume Filters

Want to help with laser cutter maintenance? You now don’t need to be on the laser committee to help with cleaning and changing laser filters, and it needs to be done every couple months. In fact, it needs to be done right now, so any volunteers would be super appreciated!

Here’s how, using pictures I took last time I took it on.

First, grab an 11mm socket and a drill to unscrew all the bolts. One of them does nothing and is just there for looks and moral support.

You’ll find 3 filter types in there, the air flows from the bottom towards the top. First is a course pre-filter sponge, then HEPA filters and finally beds of charcoal.

Starting with washing the pre-filters, I find the least dusty way is to plug the sink with something, gently place the filters in there, and fill the sink until they’re submerged, trying to kick up as little dust as possible. Once submerged they’re good to go for a good few rinses. Drain them off and place them back in the box.

Next, grab the 4 HEPA filters and chuck them in the dumpster, replacing them with new ones.

That’s pretty much it, maybe wipe down the inside of the box with a damp cloth and put the doors back on. Don’t torque the bolts too tight.

The charcoal trays don’t need to be changed every time, just when they’re really clogged. They have to be brought out to the alley and dumped in a garbage bag, and filled with new charcoal.


Thanks for this guide! I got some noob questions…

  • How do I tell if the filters need cleaning? Do we have a differential pressure sensor or similar? What is the threshold?

  • Do we have spare HEPA filters in the space? If so where are they at home?

  • How do I know if the charcoal trays are clogged (I never looked at them, maybe it is obvious)? Do we have spare charcoal handy?

I got the laser booked for an hour today 6-7pm. Since I plan to get some use of the laser in the near future, we could use that time window.

Since I haven’t been in the space much recently, I’d prefer to team up with someone that knows the space better, though. Help find tools, etc.

Anyone interested in teaming up and giving this a try today?

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You can usually tell that the filters need cleaning when you can smell smoke while cutting, since it’s not being effectively vented. There’s a water gauge on the exhaust fan, but I’m not sure what the threshold would be for that.

There should be a couple packs of 20x25 filters near the filter box, if they’re not there they might’ve been moved to the furnace (beaver) room

The charcoal gets very visibly caked in dust, last time I changed it you could almost not see the charcoal anymore. I’m not sure if we have more replacement charcoal, check under the laser, if not we’ll get some more.

If it helps, the sockets are in the red toolbox next to the hand tool shelf, and the drills are in the woodshop. Thanks for the initiative, it’s super appreciated!


Also, wear a good mask/respirator


Thanks for the instructions! Worked just fine. Filters cleaned / replaced.

The coarse filters are kinda hard to put back in place, since they are just hanging in the air. Especially if they are a bit heavier when still moist. I hope they won’t fall down. Some sort of grid shelf thing would be nice :thinking:

The water gauge was about 1 1/4” before and dropped to 3/4”. Very rough guess through. Couldn’t get close enough to actually measure.


Yeah we need new pre-filters, those ones have lost their shape. I’ll arrange for new ones as well as more charcoal.

Thanks so much for taking that on, seriously.


Any idea where to get the prefilters? Also the charcoal?

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I’ve seen the pre-filters at home depot, and not sure where we get the charcoal, but it’s just standard activated charcoal pellets


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