I keep reading about Corsi–Rosenthal boxes as DIY air purifiers that outperform all commercially available air purifiers. You literally only duct-tape four HVAC filters together and slap any regular PC fan onto them. US-Americans recommend the brand #Filtrete for MERV-rated HVAC filters, but in Europe that brand costs at least twice or thrice as much as in the USA. Are there any equivalent affordable HVAC filters in Europe with a MERV rating of 8 or 13? Or do I simply have to swallow the additional cost because HVAC filters aren't as ubiquitous in Europe as they are in North America? #DIY #CorsiRosenthalBox #CorsiRosenthal #HVAC #HEPA #MERV #AirQuality #AirPurifier #AirFilter