Ulvac CRYOPUMP CRYO-U Series Instruction Manual page 18

(2) Gases exhausted from cryopump have pungent odor, similar to that produced in
arc welding operation.
Large volume of ozone may invite an intense explosion. If ozone has been pumped
with the cryopump, the following safety precautions must be taken.
1. Perform regeneration more frequently to minimize the amount of ozone captured
in the cryopump. Required frequency varies depending on the oxygen flow rate or
other process conditions.
2. Minimize the flow rate of oxygen gas to the extent it does not affect the process.
3. Make sure the safety again when the process is changed, as it might bring
increase in ozone generation.
When using oxygen as a process gas, appropriate safety precaution and measures must
be taken with reference to "6. Regeneration after pumping flammable, explosive, or
combustion enhancing gas".
6. Regeneration after pumping flammable,
explosive, or combustion enhancing gas
When regenerating the cryopump after pumping flammable, explosive, or oxidizing gases,
those gases must be safely vaporized again and exhausted. Following safety measures on
the regeneration method are extremely important for employing the cryopump safely.
Please take proper safety measures with both hardware and software. Also, note that such
hazardous gases may be produced as by-product in the vacuum chamber as a result of
plasma reaction.
1. Safety measures for regeneration
Following are the safety measures that customers are required to supply and
implement regarding regeneration process after pumping flammable, explosive, or
oxidizing gases. Refer to Figure 2 and take necessary measures. You may have to
take additional safety measures depending on the kind of the gas used, the process
conditions, or the environment used. Be sure to take required and sufficient safety
precautions according to actual conditions.
S-6 ULVAC CRYOGENICS INCORPORATED