MVHR and bonfires / pesticide spraying?

[flanagaj]

Apologies if these questions are rather stupid, but how good are MVHR systems at dealing with external smoke in the atmosphere and also the vapour that you get from crop spraying.  I am considering installing one, but really need to understand whether the system will handle these pollutants or whether they just get drawn in and dispersed across the whole house?

[Russdl]

We live next to a field. When they are spraying we turn it off, also when they are ploughing, just for the dust.
 

All around us are houses with wood burners/open fires and not far away is a big pig farm that, on occasions stinks to high heaven. We’ve never turned it off for these events and never noticed anything indoors. You’ll be fine. 

[shuff27]

We're also next to fields but find neighbour's BBQs more of an issue.  Our Zender can switch ventilation mode from 'balanced' (i.e. normal supply & extract operation) to extract only via the app - this mitigates the issue effectively.  It runs automatically on a timer (1 hour by default) so you won't be deprived of fresh air if you forget to switch it back!  I'm guessing that other MVHR brands would have the same facility.

[ProDave]

We have no issues with stoves or similar.  But just over the neighbours boundary is his discharge from his septic tank.  On one of those dead still nights the "pong" from his ST hangs around and gets drawn in by the mvhr and the air in the house starts to smell stale.  If we notice that I turn the mvhr off until the wind picks up a bit.  Clearly the filters are doing nothing to stop that sort of pong.

[Duncan62]

If you're sensitive to air quality, it may be a problem.

 

I am.

 

Going to attempt to mitigate this with a chuffing huge carbon filter on the air intake to the house.

 

Something like:

https://www.globalairsupplies.co.uk/product/carboair-100-filter/

 

A big one with a large surface area and bore should not cause too much extra work for the MVHR.

[Kelvin]

We didn’t fit a wood burning stove because morally it seemed hypocritical to fit MVHR and a stove that pumps smoke into the atmosphere. We are fortunate in that we only have one neighbour who is only there once a month and the fields behind us aren’t arable so no spraying. 

[saveasteading]

1 hour ago, ProDave said:

  On one of those dead still nights the pong" from his ST hangs around

Is this a really primitive old tank? Even so, the 'burps' from it should expel through a vent where it doesn't cause bother, and the outfall be kept underground.

I expect something is wrong, eg the waste isn't fully treated and should go on to a big herringbone drainage system. 

The jcb driver who lifted in our tank said he'd never seen a herringbone system like ours, and most just put in a rubble soakaway or chuck it in a ditch.

Then the bco doesn't question it.

[MJNewton]

20 hours ago, flanagaj said:

I am considering installing one, but really need to understand whether the system will handle these pollutants or whether they just get drawn in and dispersed across the whole house?

 

It will handle such pollutants, but only insofar that it will indeed happily draw them in and distribute them around your house! Unfortunately, likely more effectively than if you were just passively ventilated.

 

A continuous controlled supply of fresh air was one of the motivations for us retrofitting MVHR and so it was to much concern when our (friendly and perfectly pleasant) neighbour opted to fit a woodburner... Panic set in and fearing certain death from them lighting the thing up I rigged up an air quality sensor inside the supply manifold which, if a particular threshold of PM1/2.5/10 was reached, would 'trick' the MVHR unit in to frost mode which keeps the extract going but cuts the supply for 10 minutes before reassessing the situation. It works really well and since fitting it we've never once noticed even the slightest whiff of smoke even when conditions (wind in the wrong direction, overly damp wood etc) might otherwise have potentially caused us to do so.

 

However, and this is probably he biggest point I'd like to make, not only did I fit an air quality sensor inside the supply manifold but put one inside the house and that has made me realise that we almost certainly create as much pollutants (assuming all particulate matter of a given size is equally harmful?) ourselves every day from cooking than what the neighbour's woodburner some distance from our MVHR inlet might do and so have really become quite chilled about the matter!

[flanagaj]

Thanks all.  I was hoping I was going to hear "you don't get any smells as the filtration is so good".   On that basis, I think I might re-evaluate whether I should install one or not.  

[MJNewton]

1 minute ago, flanagaj said:

Thanks all.  I was hoping I was going to hear "you don't get any smells as the filtration is so good".   On that basis, I think I might re-evaluate whether I should install one or not.  

 

With the right filtration things might be different, but mine are just standard G4 filters so wouldnt do anything for smoke.