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Ventilation: MVHR air quality, putting an air-purifier / filter inline

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  1.  
    • CommentAuthorSwarm
    • CommentTimeMay 14th 2023 edited
     
    I monitor the PM levels in our MVHR fed house and can see some high peaks when people are burning stuff.

    I didn't have the sense to plan for this when the MVHR was installed and have been looking at ways to modify it cheaply and easily, to reduce PM levels.

    My first attempt was using fairly large vacuum dust bags on the MVHR room outlets. This worked fairly well and after a couple of months the insides of the white bags have turned grey. Unfortunately, I share the house and can't live a hermit lifestyle and there's inevitable questions about why we have bags / pillows on our ceilings!

    I'm thinking of changing the MVHR system to have a DIY box in the attic, which would contain an IKEA air purifier.

    This would be on permanently and probably attach to the distribution box for all the room outlet. My reasoning for using a purifier is that the 14W fan could help maintain a good airflow from the main MVHR unit to the rooms. If I just put a filter there, the main fan may have to work hard.

    Concerns are it could be fiddly to set up and the IKEA fan probably isn't designed for 24/7 use and could possibly be a fire risk.

    Another option I suppose could be to build quite a large filter array of 2/3 filters horizontally and just have that inline without any additional fan, as the increased surface area would be less resistance for the main fan.

    Any thoughts from folk wiser than me much appreciated.
  2.  
    I would start by asking the MVHR manufacturer if they have a recommended solution
    • CommentAuthortony
    • CommentTimeMay 15th 2023
     
    I use HEPA paper filters, it is near impossible to remove the very small particulates sub 2.5 and the smaller they are the more harmful.

    You are up against it! Electrostatic filter might be the way to go after a physical one.
    •  
      CommentAuthordjh
    • CommentTimeMay 15th 2023
     
    Posted By: SwarmI monitor the PM levels in our MVHR fed house and can see some high peaks when people are burning stuff.
    'Burning stuff'? Cigarettes, candles, coal fire, cooking??? Or what?

    Generally our approach is to stop burning stuff. As well as the PMs, burning generates gases you don't want. Or do you mean burning stuff outside the house? Again, simplest solution is to stop doing it within range of the MVHR intake. The law can help if necessary.

    If the PM is coming from outside the house then you want to stop it BEFORE it reaches the MVHR fans and heat exchanger. That's why the MVHR filters are before everything else. So any additional filter needs to be before that, in the intake duct. I think but don't know for sure that what you need is a HEPA filter. As PiH says the first stop is to ask the MVHR manufacturer/supplier about recommended solutions.
  5.  
    Posted By: Swarmwhen people are burning stuff


    presumably other people's bonfires or stoves. It goes on a lot around here, one neighbour burns plastic silage wrap, another actually burns a muckheap rather than just letting it compost down to a useful product. I don't begrudge people the odd bonfire, but these are really antisocial as they tend to be smouldering acrid things for days on end, rather than one big hot burn and it's all over.
    • CommentAuthorrevor
    • CommentTimeMay 15th 2023
     
    Posted By: Dominic Cooneyone neighbour burns plastic silage wrap,


    This is highly illegal. The farmers in my vicinity have their plastic wrap, drums and fertiliser bags collected by a licenced waste contractor. Your neighbour should be reported to the council environmental department. Fortunately we do not have the problem, smells from muck spreading particularly digestate which can have quite pungent smells from volatile fatty acids, can be a problem sometimes. We do not run the MVHR in those situations.
    • CommentAuthorSwarm
    • CommentTimeMay 16th 2023
     
    Thanks everyone. Yes the problem is people burning wood for heat, despite being on gas. Even when it's warm outside, people are still lighting fires. Then there's garden fires and traffic too.

    I'm loath to start taking apart my professionally installed MVHR and installing additional filters before the heat exchange unit, if there even is space for that. We rely on the MVHR and can't be without it for long. The manufactuer solution would probably be for me to upgrade to one of their newer units which have additional filters built in. That would not be easy either and I'm not sure a new unit would even fit through the loft hatch!

    My latest plan is to move the Vacuum dust bag approach to the other end, where the airflow pipe leaves the distributor box by the MVHR. If I can shape the dust bag into a narrow wind sock shape, there will be a lot of surface area in each pipe, reducing the resistance hopefully. I know it sounds wacky but I am confident it will work and there's not much interference with the setup overall.
    • CommentAuthorRobL
    • CommentTimeMay 17th 2023
     
    Activated carbon filter? Perhaps you can try putting one after the conventional particulate filter on the air intake of your mvhr? I gave my Uncle a large recirculating "air purifier" with an active carbon filter - he uses it on days when his neighbours burn wet wood (most of the time it seems). He says it works really well. It has a black activated carbon filter in it, from memory 300x400x8mm.
    •  
      CommentAuthordjh
    • CommentTimeMay 17th 2023
     
    If you don't ask them, you have no real idea what they might suggest.

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