Designing of Vacuum chamber

Dear Forum members,
Please help me in designing the size of the Vacuum Chamber(in volume "cc") for our Application. We measure the partial pressure of Hydrogen gas at Vacuum chamber. The maximum amount of Hydrogen released to the Vacuum chamber will not exceed 1 Centimeter Cube (It may vary between 0-1cc).The Hydrogen gas is released from a chamber which is at 600-700 degree C to the vacuum chamber. We will have to continuously monitor the Partial pressure of Hydrogen that is measured with the help of pirani gauge. The Vacuum chamber is maintained at a pressure of 0.1 mbar through a Rotary Vane pump and is set at that pressure level.Now Hydrogen will be released to the Vacuum chamber. There will be increase in pressure value in the chamber due to Hydrogen. (The maximum Hydrogen released will not exceed 1cc). We like to control and keep the Vacuum Chamber temperature at 80 ºC (±5 ºC).
The difference in pressure has to be monitored. The pirani gauge specification is :
Max pressure = 100 mbar and Min pressure =0.001 mbar

Please advice / Help me in designing the Vacuum Chamber for my application
(What Volume Vacuum Chamber will be good for my application and material to be
used).

Regards,

Rajesh...