DIY HEPA filtration system for travel

[runcyclexcski]

It's been a while since I posted on my DIY asthma engineering projects here.

Some background: I've been on Xolair for 7 months now, and I am gradually gaining confidence to walk and drive 1-2 hrs from where I live, without checking the location of the nearest hospitals along the way. I still sleep in a HEPA/charcoal filtered air tent (DIY). I manage to get some exercise on my stationary bike: I breathe through a DIY ventilator that blows HEPA/charcoal/humidified/warmed air into a mask. Been tapering down steroids from 20 mg to 5 mg a day, and just checked my cortisol levels. They say 170 nM (correct units?) which they are happy with. Managed to lose 4 kilos in 2 months -- it's slow going, I hope I can stick to it -- I have 12 kilos to go to my pre-sickness weight.

Another news is that my wife and I are driving across the Channel next month -- my first attempt at international travel since the pandemic. I intend to wear an FFP3 mask everywhere, but hotels have always been a problem -- odors, dust, carpets etc -- and sleeping in a respirator just does not work for me (tried that many times). So I built a HEPA/charcoal air purifier which is more portable than what I have at home. It's not tiny, but it fits into my car and can be rolled into a hotel room (weights about 20 kg). It's all stainless steel and aluminium (regular air purifiers are made of plastic which itself has a smell). It blows clean air into a small treking tent (Sea to Summit 2-person) through a 150mm flexible duct which packs small, too. The tent is small enough to be set up in a hotel room -- on the bed, or next to it. It also can be run from a battery and an inverter (about 100W), so I can potentially use it on camp sites as well. Picture of the air purifier is attached.

[Jock-salmon]

I think this is amazing and thank you for sharing. I have 2 Hepa filters, at home, made by Puremate. I use them when we have visitors and if pollen is bad / farmers are harvesting crops nearby, etc. I wish I had your skills, expertise and ingenuity to just go ahead and make one. Well done.

[runcyclexcski in reply to Jock-salmon]

Do you have the filters just in case visitors have allergies? That's very considerate!

My experience with filters goes back to working in a government lab; they told me how to make "clean rooms" for nannotechnology labs. Building air purifiers is not that difficult, actually; maybe I should publish the protocols somewhere. The main lesson I learned is that the purifier needs to have a outlet tube which can then inject the clean air into the space where one needs the clean air the most. That is usually the bedroom for people with allergies, since one spends ~8 hrs a day immobile. I like tents, but small bedrooms with minimal furniture work, too. The requirement of the output into a tube greatly narrows down the selection of air purifiers. They also showed me how to measure the filtration efficiency (laser particle counters used to cost many Ks, but now they are much more affordable.... basic ones at least). I then used their laser counters to test a few filters they had in my local shop, and I found that most of them did not fit a HEPA standard. At the time, IQAir was a good brand, but they since then "optimized" themselves, and their HEPA filters now emit a strong odor (bad news for asthma), despite costing 1K+! The fact that the same brand can suddenly change their process finally lead me to building my own machines.