Initial DIY Cleanroom Experimentation

In It May Be Possible to Improvise A High Grade Bioshelter, Adin Richards discusses the possibility of improvising defenses against an environmental threat such as mirror bacteria. He gives an exploratory overview of why it might be possible to apply materials and equipment people often already have in their houses to pressurize all or part of a house with filtered air. It would be great if this were possible, but with all the ways for an improvised system to fail I'm pretty skeptical. I decided to try a simpler version, testing how much I could positively pressurize a single room with a relatively powerful HEPA air purifier (AirFanta 3Pro. This is close to a best case, since most people won't have something as good as an AirFanta. My first question was whether the AirFanta can pressurize much of anything, since it uses axial fans and these can stall when facing excessive pressure: (By Prj1991, via Wikipedia) To measure the pressure delta I was going to need some kind of manometer.…