A340 Crew rest module.
 

Does anyone have any definitive info on the lower deck A340 crew rest module, specifically relating to the condition of 'Low Air Flow'? My information was that when a condition of 'Low Air Flow' exists an alarm and warning light activate in the module and it's occupants should leave and not return until the air flow returns to normal. Can anyone briefly explain the how the ventilation system works, what could cause the low flow situation and whether it is necessary to evacuate the module in a hurry, or at all? Is it permissible to return to the module with the alarms still activated, and is there a means to ascertain whether the alarm was spurious or not?

What the AMM says:
 

D. Operation of the Lower-Deck Mobile Crew-Rest (LDMCR)
Compartment-Ventilation
The ventilation and individual air supply comes from the cabin air-supply
ducts for areas 5 and 6. It flows through the LDMCR isolation-valve 216HG.
From the isolation valve, the air flows through the air heater (Ref.
21-63-00) into the LDMCR.
The flow sensor measures the airflow through the air heater in the
ventilation duct of the LDMCR.
If the airflow into the LDMCR is not correct the flow sensor gives a signal
to the buzzer and to the LEAVE MCR signs.

..I don't suppose it's necessary to rush out screaming, but if you were sound asleep, the buzzer will wake you up. Without fresh air supply into the MCR, and with 8 bodies respirating, the CO2 levels would definately be increasing!

Opening the hatch to the LDMCR makes 2 micro-switches.. both must be made for air to flow.
The alarm is so loud that the lights "Leave Crew Rest" seem irrelevant.
Increasing CO2 is a problem but doesnt necessiate a dis-robed scramble up the stairs. A more serious situation would be a cargo fire (The LDMCR is fitted between the fwd and aft cargo compartments). Not only is airflow shut off during the ECAM actions but the is a the possiblity of fire extinguishing agent entering the LDMCR. In this case more urgency is obviously required.

The alarm is significantly loud to 'worry' the pax in the first few rows of the aft economy cabin!

The ECAM procedure requires evacuation of the lower deck crew rest (which is in fact in the aft cargo compartment) prior to firing the cargo bottles, so the agent seeping in shouldn't be an issue. But yes, once smoke is detected in the compartment, the isolation valve will close, so the buzzer would be an early wake up call! What's wrong with a partially robed hostie running through the cabin anyway?