Air accumulators provide reservoirs of air so that props have air nearby when they need it instead of having to wait for it from the compressor.  When props that use a high volume of air (such as blasters) need a lot of air they will draw it from everywhere they can get it.  If you don't want those props steeling air from the accumulators then check valves should be installed.  Check valves only allow air to flow in one direction.