Ventilation for dyno room

This winter my plan is to construct a dyno room so I started looking at how to vent the room. Dynojet recommends an intake fan with a cfm rating that is at least 7 times the volume of the room. They warn about pressurizing the room throwing off readings and to install an equilazer box. They mention the box size is calculated based room size and fan size but do not share that calculation. I'm curious if anyone has more information on this?

Extraction fans are even more important.

https://dynomitedyno.com/tech-corner/cell-design/

I agree with Dom. Extraction is really key to your health, tuning accuracy, maintaining reasonable temperature in the room and of the vehicle components. With sufficient extraction, some cells simply have a passive inlet opening to the room and the extraction fans pull air from the inlet, past the vehicle, to the extraction points. This is sometimes augmented with fans to direct air at specific areas needing extra airflow. If you get the exhaust side working really well, and proper room inlet placement, the inlet side won't require much equipment. This also lets you make the room smaller, since there's less stuff in it.

In terms of airflow, cycling the air in the room every 10 seconds works pretty well for dyno power pulls on semi clean vehicles, every 6 seconds is more ideal for emissions work or very high HP vehicles with massive exhaust flow. Extremely dirty vehicles like some diesels may warrant even faster extraction, but that's not something I get into so I couldn't comment on specific needs. Dynojet's suggestion puts you at around 8.6 seconds.

When you measure a room then look at blower/fan pricing, you quickly realize having an overly large dyno cell will cost you a bundle, so keep room volume only to what you need. Ceiling height is often the area of largest waste, meaning it's often higher than it needs to be, and that adds a lot of volume.

If you want to see what I feel is a good example of this in a room rather than a cell, I think Litchfield Motors has done a fantastic job:

https://www.litchfieldmotors.com/dyno/

In terms of cells, here's an example made by Noise Barriers for Jay and the crew at Real St.:

https://www.youtube.com/watch?v=NJn4Ff_ysq4