In the above formula:

In the above formula:
V = capacity of fan [m3/h]
m = charge of refrigerant in system [kg]
However, the number of air changes per hour shall not be less than 40.
Where refrigeration systems using ammonia are installed in rooms equipped with an effective sprinkler
system, the minimum required capacity of the fans indicated above may be reduced by 20 %.
E.9 Spaces containing batteries
E.9.1 General requirements
All battery-installations, except for gastight batteries, in rooms, cabinets and containers shall be constructed
and ventilated in such a way as to prevent the accumulation of ignitable gas mixtures.
Gastight NiCd-, NiMH- or Li- batteries need not be ventilated.
E.9.2 Batteries installed in switchboards with charging power up to 0.2 kW
Lead batteries with a charging power up to 0.2 kW may be installed in switchboards without separation to
switchgear and without any additional ventilation, if:
 the batteries are valve regulated (VRLA), provided with solid electrolyte
 the battery cases are not closed completely (IP 2X is suitable)
 the charger is regulated automatically by an IU- controller with a maximum continuous charging
voltage of 2.3 V/cell and rated power of the charger is limited to 0.2 kW