the cryostream flow rate is variable and can be set to either 5 or 10 l/min of gas , this equates to approximately 0.6 and 1.2 l/hour of liquid nitrogen . this means that a 60 L dewar will last for more than three days at 5 L/min . it is worth noting that different dewars have different rates of boil off , so it is worthwhile takeing this into consideration when running the cryostream and leaving it unattended forlong periods . also note that below 90 K ,the lower flow rate of 5 L/min is slowly increased to achieve the very low temperatures