In line extractor fan for K40

Hi - I’ve just purchased this really economical in line extractor fan from Amazon - I was looking at the AC Infinity, but this was a 1/3 of the price - the reviews look good and someone is using it with their laser, I only thought after that I’m dealing with hot smoke (I think?) From the laser, do you think this will be safe to use with it, I was just wondering about how hot the smoke might be and if it would damage a less expensive fan? I’m probably overthinking this too much!

Well, you’ll find out how well it works. By the time the exhaust gets to the fan it should be well mixed with room-temperature air. The only problem is if you have a fire. If you do, the fan will be the least of your worries. Do pay attention to the warnings about never running unattended and having a CO2 2kg class fire extinguisher handy!

The pictures in this post should help balance the cost of a CO2 fire extinguisher. :grin:

You might want to read this post for some recent discussion of axial vs radial fans:

@NedMan here does beautiful work and uses an axial fan. Here he shared the results of cleaning out his fan:


Thank you for the link to the other info - to be honest I’ve been reading as much as I can about laser safety, which I realised I needed a CO2 extinguisher - I had bought a foam one which I now know is conductive and not suitable for electrical fires! Also the foam will probably wreck the laser if sprayed into it :confused: … so I’ve bought a 2kg CO2 + A larger spray bottle I’ll keep next to the laser to use quickly if small flame ups happen (I don’t really like spraying water near electronics but I’ll try and keep it only on the material!) …

The fan will be going near the laser on the floor - so I’ll be able to keep an eye on it! Hopefully it won’t be too noisy!

I’ve worked out my safety procedures, this has bought my anxiety levels down abit! Hehe … here they are in order:

1.before switching on the laser:

  • Fire extinguisher close by but away from the laser - in easy reach if I needed it quickly + water bottle next to laser
  • Quick laser bed inspection - no obvious debris (full clean with hoover etc once a week / more if needed)
  • Water pump turned on - check for bubbles in the tube and release them
  • Air assist working properly and tubes nice and tight in the laser
  • Exhaust out the window and seals are nice and tight
  • Switch on - safety goggles ready to wear around neck when laser is on.

These are just what I’m doing to try and be as safe as possible, I’m sure I’m missing things! But hopefully minimising the risks as much as possible x

That 4in fan might be a bit underpowered. Does the listing tell you how much flow it delivers? Usually stated in cfm.

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I’t doesn’t say unfortunately, I’ve just read all the Q&A’s and it seems like a nice little extractor but not very powerful - I’ll give it a go and get the more expensive one after Christmas! Hopefully With the laser fan + an extra one it will do some good :crossed_fingers: x

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Ok this is really useful - didn’t think the old fan would hinder the inline one - maybe I should just stick to the 1 original fan in the laser - the exhaust tube runs around 4m to the window and does work, with no fumes in the room - maybe I’m over doing it with the extras?

The original fans are usually not very good. You can experiment and see what works best.

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I’m not sure how to turn off / remove the original fan - is it dangerous to have both running together?

(Again, thank you for answering my million questions this week!) X

Don’t think there’s any real danger in having serial fans. Could put more stress on one maybe.

If you provide a picture on your current fan we could probably tell you how to remove it. There are couple of different ways these fans are set up.

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Great, thank you - I might leave it a few days untill the new bits arrive :relaxed: x

Just found the CFM! it’s 110 :blush:

The stock K40 fan will work but eventually you will want to replace it for a few reasons.

  1. they are very poorly made and I highly recommend you open the wire connection panel and make sure the wires are secure and well connected. I used mine for a couple of days and after pulling it out I looked at it and the wires were about to fall out of the taped twisted connection.

  2. it’s better to have the fan as close to your air exhaust/exit connection as possible to keep fumes out of your house/shop should a leak occur. If mounted on the back of the machine, like stock, then there is air pressure in the entire tube length and any leak will leak fouled air. If the fan is mounted at the exit then there is a vacuum on the line and any leak will just pull room air into the tubing.

  3. use as much metal and metalic stuff on the exhaust just in case there is a fire as the exhaust will pull lots of hot stuff fumes out until something melts so you’d want that to be working as long as possible while you are extinguishing the flames.


Thank you - I can’t really have a full metal exhaust tube with my set up - for now I’m based in my dining room and put the tube outside my window - but it’s a good quality pipe with metal lining, although not much protection I’m sure if a flame were to be near it :confused: so I’ve got my super vigilant SOPs, CO2 extinguisher, small water bottle, E-switch + interlocks - hopefully that will reduce the chance of any fires occuring :crossed_fingers:

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110 CFM is a bit low in my opinion. Ideally I think you need over 250 CFM for good extraction with a moderate run of ducting. This usually requires at least a 6" fan for inline fans. When you add in the fan please be sure to let us know how it performs. :slight_smile:

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Yes it’s probably about too underpowered, I’ll do a test with and without when it arrives this week and let you know how it goes :slight_smile:

I ordered one with 150mm dia and 540m3/h. According to the specs its half the volume than we had with the previous solution. A bit more smoke is noticeable when engraving wood and cutting acrylic. But the noise is much lower than before: So a perfect solution for us.

Will report back in a year how it performs. :wink:


The fan arrived and for now the set up is ok :slight_smile: it’s not mega powerful but compared to just the lasers built in fan, it’s moving more air out - it’s also quiet so happy with that!

I can’t turn the built in fan off just yet - the screw has sheared on the back plate :confused: but as long as it’s safe to keep both running I’m happy to do that :slight_smile: x