Particle Counting in my Laser cutting room.

[OneArmedGraphic]

The Counter starting detecting (MDF cutting )particles almost immediately. It was sighted about 1m away from the machine.
I run a 400CFM grow-room style fan, porting outside. The Counts do drop quite a bit after cutting ceases.

I knew it was going to be a very interesting result but I was gobsmacked. Thankfully I have always worn a 3M respirator & today upgraded to the delux 'Cool Flow' Silicone rubber model ($99)
Within the small room I have fans pointing at HEPA style air filters, and also run a second squirrel cage fan hooked up to a grow-room air filters.

I also created a secondary 'curtain' out of thick plastic sheet, used Velcro to fasten around the pocket-style sliding door.
My Wife said it was the first time she didn't smell anything, and that the plastic was so effective it dropped sound pollution levels in the adjoining room.

Next plan is to start habitually wearing overalls or labcoat to keep the skin exposure limted.

Looooong term plan is to stop using MDF

If this interests anyone I'll do some tests with Plywood and Acrylic
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[BobL]

Thanks for posting this - next time it would be good if you were to post the results here
https://www.woodworkforums.com/f200/d...results-222282

Those particle counters are not very accurate at measuring high dust loads and my recommendation is to multiply all the PM10 concentrations by about 2.
see https://www.woodworkforums.com/f200/d...10#post2095044
The OHS level for MDF is nominally 500 ug/m^3 but given you are dealing with material that is potentially more toxic than wood dust I would be targeting normal air quality so you should be looking at <100 ug/m^3

Point a fan at anything to direct dust is a bit like herding cats ie a waste of time.

Labcoats do little or nothing for skin exposure in this scenario because the fine dust you cannot see and the formaldehyde from the MDF acts like a gas and as you move around the fine dust is pumped in and out of your clothing and will end up under you clothing. Also the particle counter will not be measuring the formaldehyde which the laser will liberate from the MDF.

Smell is not a good indicator because formaldehyde is known for damping down the sense of smell and can even lead to a temporary or permanent loss of the sense of smell. I lost mine for 6 weeks in 2002 when working outside with MDF and never smelled a thing.

You should consider installing something like a 1000CFM extraction and 6" ducting for extraction / ventilation.
It should be possible to set up extraction so you should not have to wear a mask or a labcoat.

[OneArmedGraphic]

Ok will do so. Many thanks for your reply.

I do think the Fans are helping as you can see the dust accumulate on the fans and the filter media. I used to run the exhaust through two pre-filters and they really did collect it well, but as they were homemade jobs from plastic boxes the leaks were awful.
The Machine Port is 4 inch and I connect that to a 4 to 6 inch fitting then it’s the fan and short run of metal ducting made from Kitchen rangehood ducting.

One benefit & curse is that it's a very small room, so it is able to quickly do a complete room change with the current CFM, however I'm venting out and in through sliding windows that are about a metre apart. I also don't vent up through any style of chimney, so you can imagine that dirty air has a pretty easy path to come back in again. I was reluctant to construct a Chimney as it would be visible from the street and I hope to avoid the local Council getting curious.

I suppose it's time to consider better extracting & internal & external Venting + Chimney. Or invest a lot of $$ into a BOFA Filter.

[BobL]

Ok will do so. Many thanks for your reply.
I do think the Fans are helping as you can see the dust accumulate on the fans and the filter media

Relying on what is seen is not aways a good guide as to what is going in.
A better guide will be the particle counter even if it does not have high accuracy.

What would be interesting to know is the PM2.5 concentration during and for some time after cutting plotted as a graph. The we could work out the half residence time of the dust and make better projections about long term safety. Not just for the time for cutting out one piece but for a typical working session.

I used to run the exhaust through two pre-filters and they really did collect it well, but as they were homemade jobs from plastic boxes the leaks were awful.
The Machine Port is 4 inch and I connect that to a 4 to 6 inch fitting then it’s the fan and short run of metal ducting made from Kitchen rangehood ducting.

What sort of a fan are you using. (type, size and CFM rating)

If it's not possible to change the machine port to a full 6" then adding an extra 6" duct just above the cutting head and using a Bell Mouth Hood (BMH) would be the most efficient way to collect the extra lost air

One benefit & curse is that it's a very small room, so it is able to quickly do a complete room change with the current CFM, however I'm venting out and in through sliding windows that are about a metre apart. I also don't vent up through any style of chimney, so you can imagine that dirty air has a pretty easy path to come back in again.

Yep that is exactly what will happen unless precautions are made. you can of course test this with the particle counter.

Another approach would be to take advantage of the laser cutting action whereby the outgoing air will be warmer than the incoming air. Therefore if you were to fit ply or acrylic panels to the windows with short 90º elbows, one blow pointing upwards that would act like a short chimney directing the dust out and up, and the other down and attach some 6" flexy to collect air close to the ground for teh incoming air. Even this amount of separation will tend to draw fresh air in from the sides to assist in the ventilation.

What about the door into the room? would it be possible to fit a grate into the door itself to get fresh air from a completely different source.?

[alfclp]

What type of dust monitor are you using? Specifications? As for the old saying "oils ain't oils".

I have had over 40 years in the field of dust monitoring so am quite interested in the findings.

[Lappa]

There cheap unit’s from China. A number of us bought them for a “look see”.

[OneArmedGraphic]

Yeah I got a local eBay seller & it arrived within two weeks.

[OneArmedGraphic]

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As you can see the windows are within spitting distance, so not ideal at all. Like you suggest some sort of direction chimney exhaust and shield intake would be much better way of dealing with the cards I've been dealt. We need to screen the Window also as you can see it from the street (although it'd be approx 4-5 feet drop and strategically planted hedgerow will eventually help with that)
Using a 6" 315 CFM