Dry Riser air release valves

[morph]

Hello Everyone,

Has anyone out there experienced any problems with newly fitted air release valves on dry riser installations?  The problem noticed is premature sealing of the valve, preventing the air being released as the dry riser is being filled with water.  This leaves a column of air in the top of the pipe, significantly affecting the landing valve below the top floor. 

We are informed that these valves are 'Industry Standard' but the problem is they don't work.  We are not able to source a different valve to try.

Any advice or news of similar experiences would be useful.
Thanks in advance.