How to Make a Photocatalytic Air Purifier

We write books, so we spend a lot of time indoors. When we go outside the air seems so much fresher than inside. Is there any way to recreate that fresh air feeling indoors? That's a question we've been trying to answer for a few years now. We think we've found an answer. It's called photocatalytic air purification. What exactly this means is described in the first section. The final section of this guide describes in detail how to actually make an air purifier that uses photocatalysis to remove volatile organic chemicals (VOCs) from the air.
The photocatalytic air purifier which we've created and describe here has made a positive difference to us. We set it on a table next to where we work and run it whenever we're working. When it's running, the air seems fresh, similar to having a nearby open window. It's not magic but it has reduced the incidence of itchy watery eyes, irritated throat, runny nose and general feeling of malaise that VOCs can produce.