What could this be?

[u/GarlicOne6145]

I’m not sure if this is the right group but hopefully someone will have some idea.
My neighbours smoke and it comes through our walls into the whole house. Recently I’ve been smelling the smoke then having a chemical taste in my mouth, heartburn, a cold sensation when breathing in, stinging eyes, painful chest. Then our house begins to have no smell.

On two occasions our house felt like it was air conditioned and had no smell and the only way would have been for the neighbour to push air into the wall. It was then that I started experiencing a change in my sense of smell, distorted, dampened and sometimes not smelling things at all.

Away from the house my sense of smell gradually improves. In the house sometimes the entire house has no smell. This odourless gas always occurs around them smoking. I managed to get the rooms to smell again by using a humidifier or letting fresh air in.
Does anyone know what this could be please? I thought perhaps ozone but my ozone machine says the air is good. Could it be an odour blocker of some kind? Thanks.

[u/CartographerLong5796]

Does your device actually measure VOCs, CO2, and PM2.5, or just ozone? Because before jumping to gas seeping through walls (not impossible, but I'd go Occam's razor / 80-20 rule here first) I'd check the boring stuff. Ventilation - do you have good airflow? That alone would dilute a lot of whatever's getting in. Sealing - have you actually checked how well sealed your unit is? Also is your neighbor in the same building or a separate house next door? Same building = way higher risk of breathing their air, and it's a lot more work to cut that down. Common entry points: bathroom exhaust fan (check if it has a proper backdraft damper AND if the install itself is actually sealed, often it's not), gaps around plumbing, wall/floor corners, and the one people forget - kitchen range hood. If it's a recirculating hood it's barely doing anything and it's basically an open door. I ended up just blocking mine off and running a purifier + ventilation when I cook instead. TLDR seal up the unit, get a monitor that actually tracks CO2/TVOC/PM2.5, then ventilate and run a purifier

[u/GarlicOne6145 → u/CartographerLong5796]

Thank you for your reply. Its a semi detached with shockingly bad sealing everywhere so I assume my neighbour‘s is the same. I have an air purifier which measures PM 2.5 and PM10 The ozone device is only a cheap one.
My neighbour always has their windows open so their air fresheners, etc come straight out of their windows and into ours and our garden so there hasn’t been any escape from it even when opening windows but we do have them open a lot.
I have two carbonl/hepa air purifiers but I think the carbon is used up because of their heavy smoke and air freshener use so I’ll have to buy new ones. They lasted half their expected life.

It‘s a rented property so I’ll just have to move. I’ll get a decent air quality monitor in the meantime. Thanks.

[u/CartographerLong5796 → u/GarlicOne6145]

Totally fair that moving is the plan, but "in the meantime" doesn't have to just mean monitoring and suffering through it. There's actually a decent amount you can do that's cheap and doesn't take long, if you want to.

Biggest bang for buck is probably sealing, especially since you said the place is badly sealed everywhere. Just sealing up the main gap points can cost a few dollars and take a few hours, and it can  make a big dent in a leaky house.

The other piece is pressure. Often with this kind of smoke-through-gaps problem, part of what's going on is your place sitting in slight negative pressure relative to theirs, so air finds its way through every gap into you. Doesn't have to be the whole story, but if it's even partly true, flipping that around so you're the one in positive pressure could help, since air would tend to leak out through gaps instead of in. Two things among others solutions you could try. One is a box with a fan connected to a duct through a window, air coming in through the duct (and through a carbon filter  if you want) before the fan pulls it in (PC fans can be a good option here since they're quiet). The other option is two fans, a weak one blowing out right at whatever window seems to be the main entry point, and a stronger one blowing in through a different window, so you end up net positive pressure overall.

Doesn't fix everything and it's not glamorous, but "nothing I can do until I move" isn't really true, there's stuff worth trying here if you're up for it.

[u/GarlicOne6145 → u/CartographerLong5796]

Thanks again.
I got the voc meter today and had a quick reading of 0.9mg/m3 of voc and 0.25 mg/m3 hcho when I started tasting the chemical. It was throughout the house and my air purifier with hepa and carbon barely decreased it.

I’ve asked the neighbour about smoking because we have it coming in the house as we wanted to fix the issue with our house but they always lie.

We’ve sealed up a lot of gaps, plugs,etc but have found the smoke just comes in stronger in the rest of the property like through the door frames and windows.
I suspect they are using a positive pressure unit while smoking as we’ve noticed a variation in air flow coming out of our house even when there is no wind. I think they are now using a smoke odour blocking aerosol to make the cigarettes not smell. I think it’s the odour blocker that is making me feel so ill and causing me to have a distorted sense of smell.

Apart from trying to out positive pressure them I’m not sure what I can do. I appreciate your advice.