Any experience of fireplace or chimney dampers?

I have used these

If it's only used rarely, a chimney balloon is the thing, looks like an inflatable pillow.

This umbrella product was considered niche by the dragons, and laughed off for the cost.

Why not close it for good, and install an LCD monitor and an infra-red space heater?

I have a rolled-up offcut of rockwool shoved up mine.

Thanks, but I'd ruled-out a DIY version of those because of the problems of storing a big sooty thing, and crud falling down when it's pulled from the chimney

I discounted chimellas and balloons because they're only slightly better than a made-to-fit DIY wooden panel (and it's quite a large fireplace) - storage and crud being the main problems. I'm thinking of a metal frame with a pivoted metal plate, similar to these:

Discounted because of storage, crud and size

Storage - a ballon deflates, deflate, shove it in a bag.

Crud - Is going to fall down anyway. At least with a balloon you know when it's going to.

Size - See storage and surely with a little used fire place "storage" is up the chimney. B-)

and at £15 or so you don't have to use it for long to cover the cost (assuming the fire doesn't rely on air from vents you close when not using it).

Irrespective of any mode of blocking you are going to get the crud that has fallen on the blocking mechanism dropping down when opening up again, otherwise where do you expect this crud to disappear to?

Even with a bespoke fixed design consider how it is to be cleaned.

I think they centre pivot so the crud slides off when opened.

The fixing trick is knowing that you have to take out and replace some brick above your fire opening.

An angle-iron frame around the outside with a pivoting, removable and counterbalanced plate that fits into the frame.

Possible downside.

If Santa gets stuck, there will be no presents this year.

No, it would be fixable from inside the chimney and have minimal effect on the throat when open

A crow fell down my chimney that is lined with a stainless steel double insulated liner.

Normally they fall down the open fire flues, s*it on everything and fly out of a window.

But this one came to rest against the rotating chimney damper of the wood stove, where it couldn't get out and I couldn't pull it down either. After a week the noises stopped, but the damper was jammed.

Eventually, come this winter, I lit a fire.

That cleared the blockage.

Obviously you get the chimney swept *before* you install a blocker. Then it won't drop soot when you take it out for the winter

And the crows instead of flying out of the open fireplace, will simply die, instead.

Ha! I'll wait until after Christmas to make any changes ;-) Fortunately our Covid isolation ends at 1 second past midnight on Christmas day, so we'll be able to welcome him/her/it.

Hmm. I have done a couple. Both times the best access was through the front of the chimney.

Getting a good seal with something permanent and designed to work with an open fire too isn't going to be easy.

OK. I'm going mostly by this chap: