Oil backstreaming can occur in the event of a power outage when oil from the rotary vane pump backs up through the forelines into the vacuum chamber of the turbo pump. In some applications, minor backstreaming has no impact; in others, where the purity of materials is critical, backstreaming cannot be tolerated. It is advantageous in high vacuum systems to include automatic interlocks to avoid the effects of backstreaming and contamination of the turbopump. This can happen during a power outage or other system failure. Many high vacuum systems do not have built in automatic protection mechanisms. If everything works fine, then there are no worries. It’s when unexpected events happen that a “do nothing” approach could cost time and money.