Pretty sure this is what we used http://www.firecoltd.com/detail-Fire-Door-Retainers-Architectural-Slimline-Hold-Open--Swing-Free-Universal-Emag-161-332.aspx

 

You should get a much better price than that if you push hard with them! We did 

There is a battery operated kit that releases the tread down retainer closing the door using standard closer on the sound of fire sirens, but did hear the Henry Vac triggers then?

Not cheap either, about £600 ish each door but then theres no cables.

Would have thought a prime area for retro fit wireless devices?

Door guard £120 ish.

But will close if you sneeze near it.

Sh1t imo but a last resort if you cant wire.

Went to a care home in a corridor and had to hoover up some dust all 20 odd doors came crashing shut on all the bedrooms!

They are rubbish arfur, we had some fitted and ripped out again. Constant problems with them not retaining correctly, closing at will list goes on. We were refunded no questions asked (they were installed and removed by the manufacturer) so they know they have issues

for the feedback guys,

tbh if they shut when not needed its not so much of a problem on this site, issue is with tenants wedging back doors in common parts usually because of prams or moving furniture causing fire spread hazards.