Can I leave auto vent openers in my unheated greenhouse through the winter? (Zone 6a/b)

Hi Gang!
I'm in the process of building a small passive solar greenhouse, 6' by 10', and I'm not planning to heat it. I'm in Nova Scotia, Canada, near the coast, equivalent to about Boston or coastal Maine. The maps from years ago put us in Zone 6a, but I would say we're 6b now and maybe approaching Zone 7 some winters. Between thermal mass and insulation, I'm hoping I can keep things generally above freezing in there, but this will be it's first winter, so we'll see!

I just bought 4 vent openers today from a local retailer who tends to do their homework on what they carry. The name on the box is "Thermoflor Autovent". I notice they're made in the UK. They look just like this model from Halls: https://hallsgreenhouses.com/halls-auto-vent-opener/p/63939

At the counter, a half page sheet was given to me along with the product. One of the paragraphs on it said that in areas where temps will be below freezing, the openers must be "removed and stored indoors for the winter to prevent damaging the unit". Then there were instructions given for how to thaw the units slowly if the seals happen to freeze.

The page also mentions "the gas" in the opener expanding. My first question: is there a significant difference between an opener that uses gas and one that uses wax in terms of how they handle cold? Until I was given this page, I hadn't read about needing to remove openers anywhere else while I was researching various models.

Second, I was thinking that since they're not going to be opening unless the temperature hits 55F at the vent level they won't be damaged by sitting "inert" in the cold. According to the leaflet, this is wrong.

Does anyone have experience with these type of vents and how they behave during winter?

And do you bring them in for part of the year? Has anyone had them damaged by leaving them out in the cold? I'm trying to decide whether to return them and get something different.
Thanks so much for your help on this!

Susanna said, "One of the paragraphs on it said that in areas where temps will be below freezing, the openers must be "removed and stored indoors for the winter to prevent damaging the unit". Then there were instructions given for how to thaw the units slowly if the seals happen to freeze.

I don't have any experience or even know what you are talking about.

My suggestion is to follow the instructions.

By bumping this thread may be a member with some experience will chime in.

Anyone with experience with "Thermoflor Autovent"?

I am no expert, but I did buy a couple cheap wax based openers from Amazon. I left them in an unheated greenhouse over winter in Maine. They seemed to work just fine the following year... but that was only 1 year, and I moved the next and had to leave the greenhouse I had built.

I've disconnected mine and kept them in the greenhouse over winter (where it got below freezing).  They've worked fine for two years now.  I wonder if the issue is if they are thawing and have a door pushing on them as they thaw out?

I don't know that greenhouse people in my part of the world  remove their gas openers. And, the rear hatches on cars use gas openers that survive and work at -40.

Regarding this specific model, my guess is that the seals aren't designed for cold weather, so they may shrink to a point where the gas starts to escape. If the manufacturer has flagged this as an issue, I would bring them inside.

There might be a difference between gas openers (like on car trunks) and wax openers (like on greenhouse vents).

Hey Everyone, thanks to Ann for bumping this thread and thanks to everyone for chiming in!

My husband and I have been talking about these vents - has some mechanical know how - and we've come to the conclusion, like you did Doug, that it's all down to the seals and possible gas leakage.

And Mike, I think you're right, the leaflet mentions that the opener can be damaged if there is any movement of the piston or adjustment screw while frozen and that they need to be thawed slowly. That damage could definitely happen here, with a cold night and then a vent 8 feet up at the top of the straight back wall warming up quickly as the sun starts to hit the glazing.

I've done some more reading about wax vents and I've read that the Bayliss wax cylinder vents are meant to be left out all year round. I've heard people say that they've lasted 5+ years.

What you've all said has helped me confirm my decision to return these gas models and get myself some quality wax openers that will last a lot better in the long run.
Thanks so much!!