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Thanks. Yes, I already had an output duct with two duct-fans in tandem, which removed air from the lab, directly to the outside. In a colder area such as mine, this involved a lot of heat loss, which was expensive due to my electric baseboard heaters. I think a simple opening to the outside would work about the same, which would allow the incoming air to exit the lab easily. How air-tight the lab is would make a difference. If air can escape fairly easily, and I assume it can in most labs, then it might not be necessary to add an output duct.

Thank you for sharing.
So you have air intake and "outtake" in your lab? From what I understand this blows new and warmed air into your lab, and I suppose you have an air extraction somewhere?
Thank you
Loic

After testing this for a while, I wanted to share this new air intake system for my lab, which is working well, in case anyone else is interested.

[attachment=0]P5240073.JPG[/attachment]

A 6-inch hole was drilled through the wall to the outside, and ductwork went to the filter box:

https://www.ebay.com/itm/333951840201

At the end was placed a heated duct fan called a "Hotpod."

https://www.amazon.com/dp/B00AOGTIOE?psc=1&ref=ppx_yo2ov_dt_b_product_details

The Hotpod includes a thermostat. It raises the cold air (during some parts of the year) quite a bit. (Or the fan can be run without heat.) It will take some time to install this system. It needs to be wired to a dedicated 15-amp breaker, plus the thermostat needs to be placed and wired. But it has been well worth it.