Blower assembly at termination of dryer duct...

The only blower assist assemblies that I’m familiar with are the in-line air switch activated type. This was on the end of a dryer duct that was about 39’ in length. I have no idea if this thing is adequate or not. Does anybody know anything about this type of device? Sound off please!

I found out this is a FanTech RVF 4 rated at 110 CFM. I called the company and they say it can handle four inch duct up to 110 equivalent feet. Doesn’t seem like it to me but you learn something new every day I guess.

Thanks for sharing , John. I’ve never encountered one of those.
Looks like there are a lot of inline booster fans]( on the market that are similar to the ones we see on radon mitigation systems.