Pre-Filter for Log Burner Smells

[runcyclexcski]

This is an old post. I have a MVHR combined with a DIY carbon (10 kilo can) and a HEPA filter (12"x12"x10"); the fine filters are installed downstream from the MVHR, and there is an additional booster for the input air. I have severe pollen allergy in the summer, and I am very sensitive to wood/weed smell in the winter, and the filtration helps tremendously (otherwise I would have to go to the hopsital all the time). In the summer, I bypass the MVHR and run the filters directly.

 

Considering how much condensation there is the MVHR in the winter (which I am still figuring out how to properly deal with), I am glad I installed the fine filters downstream of the MVHR. Otherwise all my fancy HEPA and carbon filters would be soaking wet. The innter coarse filter in the MVHR is still there, I am hoping to replace it once a month (if I source the generic fabric). With the fine filters downstream from the MVHR, all the condensation gets captured in the MVHR and the air downstream from the MVHR is warmed to abt 16C which is well above the dew point in the flat.

 

If I had to use a commercial product I would prob put in an IQAir box with a 200mm duct and its own carbon bed (about 2.5 kilos), I believe it's about 1K, and one can adjust the air flow between 50 and 250 m^3 per hr. I ended up making my own, b.c. IQAir's HEPAs have their own smell. 

 

One needs to be careful with the carbon itself serving as a source of particles. Some people use horiculture carbon as a cheap replacement (not meant for indoor air applications), and end up breathing the fine carbon dust. That carbon can be caught with a HEPA or a Filtrete, but a laser particle counter is necessary to ensure that it's safe. IQAir has a HEPA downstream from carbon, so it's safe in terms of carbon-emitted particles.

 

Re: cheap car filters: I found that the amount of carbon in car filters is negligible to have any effect for an extended time, if the unit operates 24/7. Unless one is willing to replace the car carbon filter every week.

Edited January 2 by runcyclexcski

[skhell]

2 hours ago, runcyclexcski said:

This is an old post. I have a MVHR combined with a DIY carbon (10 kilo can) and a HEPA filter (12"x12"x10"); the fine filters are installed downstream from the MVHR, and there is an additional booster for the input air. I have severe pollen allergy in the summer, and I am very sensitive to wood/weed smell in the winter, and the filtration helps tremendously (otherwise I would have to go to the hopsital all the time). In the summer, I bypass the MVHR and run the filters directly.

 

Considering how much condensation there is the MVHR in the winter (which I am still figuring out how to properly deal with), I am glad I installed the fine filters downstream of the MVHR. Otherwise all my fancy HEPA and carbon filters would be soaking wet. The innter coarse filter in the MVHR is still there, I am hoping to replace it once a month (if I source the generic fabric). With the fine filters downstream from the MVHR, all the condensation gets captured in the MVHR and the air downstream from the MVHR is warmed to abt 16C which is well above the dew point in the flat.

 

If I had to use a commercial product I would prob put in an IQAir box with a 200mm duct and its own carbon bed (about 2.5 kilos), I believe it's about 1K, and one can adjust the air flow between 50 and 250 m^3 per hr. I ended up making my own, b.c. IQAir's HEPAs have their own smell. 

 

One needs to be careful with the carbon itself serving as a source of particles. Some people use horiculture carbon as a cheap replacement (not meant for indoor air applications), and end up breathing the fine carbon dust. That carbon can be caught with a HEPA or a Filtrete, but a laser particle counter is necessary to ensure that it's safe. IQAir has a HEPA downstream from carbon, so it's safe in terms of carbon-emitted particles.

 

Re: cheap car filters: I found that the amount of carbon in car filters is negligible to have any effect for an extended time, if the unit operates 24/7. Unless one is willing to replace the car carbon filter every week.

 

That experience is a great contribution for the forum!

What carbon did you use to make your filter? Can you share some pictures of the filter?

The the carbon filter is upstream of the MVHR unit? 

 

I also saw the Nuair IAQ-BOX, it's quite interesting, but it's quite expensive. According to the documentation, it seems that the particulate filter is before the carbon filter (https://www.nuaire.co.uk/documentstore/IandM/671811.pdf)

 

 

At the moment I am considering the Blauberg Clean Box (https://blaubergventilatoren.de/en/product/clean-box-200-g4-f8-carbon), or some other equivalent as the Vents FB K2 (https://ventilation-system.com/product/fb-k2-200-g4-c-h13/#downloads), or the TECNA ISOBOX FB-K2 (https://tecna.es/todos-los-productos/comercial-e-industrial/filtracion/isobox-fb-k2/), which is easier to find in Portugal. I still have doubts if a system like this will be able remove the smoke smell or not...

 

 

Edited January 2 by skhell

[skhell]

On 25/12/2024 at 18:48, MikeGrahamT21 said:

It’s on the intake side, before it reaches the ventilation unit. Keeps all the ductwork nice and clean too as there’s so much crud comes in from outside

 

@MikeGrahamT21 Is the carbon filter in the Blauberg Cleanbox made of small carbon granulates, like the following one?

[MikeGrahamT21]

4 hours ago, skhell said:

 

@MikeGrahamT21 Is the carbon filter in the Blauberg Cleanbox made of small carbon granulates, like the following one?

 

Yes thats the one. The openings are hexagonal on mine, presumably to increase surface area

[runcyclexcski]

I have not tried the blauberg clean box, but the price is already pretty low as is (I found that it costs under 400 EUR?). It looks solid, and it should deal with the smell at least for 6 months (I doubt it would last more than a year). My IQAir carbon bed is about 2.5 kg, and it needs replacement in about 6 months at air flow of 150 m^3 per hr.

 

I have two possible concerns about the clean box:

 

-- the UV lamps will generate ozone which, in principle, should be reduced 10-fold by the carbon bed, but if you do not replace it on time, and/or do not measure the ozone in the output, it may be harmful in the longterm. Ozone meters are not cheap (mine was about 1000 EUR). Personally, I would disable the lamp, or regularly check the ozone output. The "safe" levels are about 50 ppb, but double-check this number. If the lamp generates 1000 ppb ozone, then, after the carbon, it will be at about 100ppb which is high for long-term exposure.

 

-- The lack of an additional filter downstream from the carbon could be concerning. In principle, if there are no vibrations, there should be no carbon dust emitted by it, but if one does not have a particle counter, one cannot tell. I would add an additional electrostatic filter downstream from that and verity the result.

 

I would not bother with DIY if the clean box works for you, since the box is very cheap at <400EUR (as long as you can source the filters for it).

 

Here is a pic of my filter, it costed me way more than 400 EUR to build :), but I like it b.c. it uses generic parts, and I can upgrade/replace parts as needed. E.g. my initial Blauberg blower proved weak, so I replaced it with a 2x bigger unit. I used 3030 T-slot profiles to bolt it together. The filter is downstream from the MVHR. The MVHR is next to the window, then there is a 200mm duct that goes across the room to the filters (the wider the duct, the better). The carbon bed is not shown, it's further downstream from the blower. I used a 7-kilo horiculture in-line filter ("AIRCLEAN"), and an additional 2.5 kilo IQAir carbon filter downstream from that, and two 3M MERV13 30x30 cm filtretes downstream yet (to capture carbon dust). 

 

The filters drop the rated "free" air flow of the blower by about 2-fold, and I have so far not had a blower fail after 2 years of 24-7.

 

This is the inline carbon filter:

https://www.visionofhemp.ch/shop/en/can-filters-inline/8966-can-filter-can-inline-425-125mm-8718819995234.html

 

This is the IQAir carbon filter downstream from it (the horiculture filter itself had a smell, but it does bulk of the work).

 

https://www.amazon.de/-/en/IQAir-V5-Cell-Filter-Gas-Odour/dp/B0007U46T4

 

These are filtretes to scrub the carbon dust, and also used as pre-filters:

https://www.filtrete.com/3M/en_US/p/d/b00040201/

 

HEPA was from here:

https://www.ozcon.co.uk/products/hepa-filter/

They are about 150EUR each, and I got a pack of 10. The manufacturer is MGT (Turkey), and the HEPAs are very solid (stainless steel with separators), verified with a particle counter. The part number can be obtained from this PDF; my HEPA was 305x305x150 and rated as H13

 

https://www.ozcon.co.uk/wp-content/uploads/2021/07/High-Temperature-Resistance-HEPA-Filters.pdf

 

 

 

Edited Friday at 15:59 by runcyclexcski

[MikeGrahamT21]

7 minutes ago, runcyclexcski said:

I have not tried the blauberg clean box, but the price is already pretty low as is (I found that it costs under 400 EUR?). It looks solid, and it should deal with the smell at least for 6 months (I doubt it would last more than a year). My IQAir carbon bed is about 2.5 kg, and it needs replacement in about 6 months at air flow of 150 m^3 per hr.

 

I have two possible concerns about the clean box:

 

-- the UV lamps will generate ozone which, in principle, should be reduced 10-fold by the carbon bed, but if you do not replace it on time, and/or do not measure the ozone in the output, it may be harmful in the longterm. Ozone meters are not cheap (mine was about 1000 EUR). Personally, I would disable the lamp, or regularly check the ozone output. The "safe" levels are about 50 ppb, but double-check this number. If the lamp generates 1000 ppb ozone, then, after the carbon, it will be at about 100ppb which is high for long-term exposure.

 

-- The lack of an additional filter downstream from the carbon could be concerning. In principle, if there are no vibrations, there should be no carbon dust emitted by it, but if one does not have a particle counter, one cannot tell. I would add an additional electrostatic filter downstream from that and verity the result.

 

I would not bother with DIY if the clean box works for you, since the box is very cheap at <400EUR (as long as you can source the filters for it).

 

Here is a pic of my filter, it costed me way more than 400 EUR to build :), but I like it b.c. it uses generic parts, and I can upgrade/replace parts as needed. E.g. my initial Blauberg blower proved weak, so I replaced it with a 2x bigger unit. I used 3030 T-slot profiles to bolt it together. The filter is downstream from the MVHR. The MVHR is next to the window, then there is a 200mm duct that goes across the room to the filters (the wider the duct, the better). The carbon bed is not shown, it's further downstream from the blower. I used a 7-kilo horiculture in-line filter ("AIRCLEAN"), and an additional 2.5 kilo IQAir carbon filter downstream from that, and two 3M MERV13 30x30 cm filtretes downstream yet (to capture carbon dust). 

 

This is the inline carbon filter:

https://www.visionofhemp.ch/shop/en/can-filters-inline/8966-can-filter-can-inline-425-125mm-8718819995234.html

 

This is the IQAir carbon filter downstream from it (the horiculture filter itself had a smell, but it does bulk of the work).

 

https://www.amazon.de/-/en/IQAir-V5-Cell-Filter-Gas-Odour/dp/B0007U46T4

 

These are filtretes to scrub the carbon dust, and also used as pre-filters:

https://www.filtrete.com/3M/en_US/p/d/b00040201/

 

HEPA was from here:

https://www.ozcon.co.uk/products/hepa-filter/

They are about 150EUR each, and I got a pack of 10. 

 

 

 

 

I've yet to change my carbon filter in the blauberg, its been in there about 3 years now, with no noticeable smell ingress, when there is active smoke smell outside. My cleanbox sits pre-MVHR, since i wanted to take advantage of the H13 HEPA before it got to the MVHR, and is in a cold loft space.

 

There is a G4 type filter on the intake in the MVHR which i put in there, firstly to fill the space where it goes, and secondly to ensure the cleanbox did as it should, filter has remained clean and looks and smells as it did brand new out the box, so not convinced there is any carbon dust, nor should there be with the pelletised system.

[runcyclexcski]

Mike, the carbon dust I was measuring was in the micron range; I do not think that would settle and form a visible soot on a flat surface of the exchanger. I do see a black dusting on my downstream filtrete post-filters (meant to remove the carbon sust) from carbon. In all air purifiers I've dealt with there was an additional post-filter after the carbon, and it was consistent with my particle counter measurements. The amount of carbon dust was much higher if there was vibration in the bed (at least 10x higher).

 

With regards to the MVHR, I have decided that I can always wash the exchanger cube with tap water and wipe the insides of the unit, if needed. Observing how much condensation there was in the MVHR, I decided that I did not want to deal with it in my HEPAs.  

[skhell]

@runcyclexcski 

That's a great setup you have there!

I have also considered a grow filter like yours, but I was concerned about the carbon dust. By what I have read in some indoor grow forums, they do tend to release some carbon dust, at least in the beginning.

 

Regarding the filters for ventilation systems, such as the Blauberg Cleanbox, I suspect the amount of dust they release should be minimal. I have seen somewhere some guys building their own carbon filters with carbon pellets and they wash them thoroughly to release all the carbon dust before assembling the filter. Here's such a case: 

 

 

 

I suspect that the carbon in the Blauberg Cleanbox or in the Nuaire IAQ-BOX is properly cleaned so it doesn't release dust (or a significant amount) 

 

I have also read somewhere,maybe in the installation manual of the Cleanbox or the IAQ-BOX that they should be mounted in a vibration free surface, as you have also mentioned.

 

I like the idea of using an extra blower to overcame all this filters. What blower are you using? Is it speed adjustable? How do you balance the insulation of new air and extraction of old air?

 

I have recently installed a particulate sensor at the intake of my MHVR system to try to detect smoke, but there is not a direct relation. When there is smoke, the particulares rise, but sometimes there are particulates and no smoke... If I go to the Cleanbox or other solution, I might install one of these sensors after the carbon filter to see the difference. 

 

I will probably install a carbon monoxide (CO) at the MHVR intake. That way I will be able to detect when there is smoke and stop the MVHR unit until I get a better solution.

[runcyclexcski]

skhell,

 

Indeed, horiculture filters release dust, this is why I put an "air purifier" grade carbon bed downstream from the horiculture carbon, plus two post-filters to contain the dust.

 

I found that the amount of dust never settles with time: vibration always brings more of it; this is the nature of the material, I guess.

 

One can get low-dust carbon pellets from manufacturers of respirator cartridges; that carbon is very costly -- I paid 400 EUR for a 20 kilo bag. I only use that for my DIY respirator and PAPR cartridges. This is prob the best carbon one can get, and still respirator makers use electrostatic fabric to capture dust from them (there is always some dust in carbon, no matter how good it is). There are "ball pan" hardness standards for carbon used in breating products, there are ASTM and EU standards for it.

 

Currently I am using this line of blowers. My local shop is in Basel, but they are available all over Europe.

 

https://www.visionofhemp.ch/shop/en/ventilator-125mm/11487-tube-fan-pk125-whsp-ectc-8594171433054.html

 

I use them b.c. they are quiet, and my wife hates the noise; the EBM Papst motors are proper. There are three speed levels. Blaubergs are about 1/2 the price, nothing wrong with them. You can get "dimmer" adjusters for regulator-free AC blowers, but dimmers emits annoying noise at low voltages (at least cheap ones I've tried  ). So I just use the three-sppeed blower instead.

 

To balance, I measure the air volume per unit time for air in/out with an anemometer (calculated using the duct cross-section). Since the outgoing air in the MVHR has much less resistance (no filters), it ends up having much faster flow than air in, which is not good for me (I like the flat to be slightly pressurized, to prevent odors from getting in from the outside). To balance it, I attach a long narrow (100mm diam) flexible duct to the "out" on the MVHR (my MVHR has 100 mm connectors) and adjust the length of the dummy duct until the air volume per unit time at the "out" duct entry is slighly less than the fiow "in" downstream from the filters. The output duct ended up about 4m long to drop the air flow 1/2. Just make sure the entry is not blocked, the dummy duct likes to act as a vacuum cleaner  and sucks itself to any surface.

 

I have never dealt with CO in the outdoor air -- unless the inlet for it is in an enclosed area, like a garage. I think smoke and particulate pollution from emitters (diesel etc) are more of a concern. And even if the MVHR gets some smoke in, washing the exchanger and wiping the insides of the unit should be easy. Or, the cube can be replaced.

 

Another concern for me is ozone in the summer (which can get to 200 ppb on hot days in my area, and inflammation in test subjects' lungs has been detected from exposure to 75 ppb --seen studies on that). Carbon deals with that pretty well. So my 7 kilo horiculture carbon catches ozone, ammonia and odors in the air (summer/winter pollutants that bother me) and the "air purifier" carbon then contains whatever dust is released from the horiculture carbon.

Edited Saturday at 15:53 by runcyclexcski