Why Is Fog or Mist Coming from My Vacuum Pump?

Seeing fog or mist coming from your vacuum pump usually means excessive moisture is being pulled into the pump during operation. This can happen if there’s moisture left in the chamber or if the vacuum system isn’t sealed tightly.

What You Can Do

1. Check for Leaks

• Make sure all connections—including the vacuum hose and door gasket (the rubber seal around the door)—are secure and undamaged. A poor seal can let moisture into the system.

2. Inspect the Door Gasket

• Wipe the door gasket clean and make sure it’s properly seated to create a tight seal.

3. Dry the Chamber

• Before starting a batch, ensure the freeze dryer chamber and shelving unit are completely clean and dry. Any leftover moisture can cause fog or mist.

4. Check the Oil (for oil pumps)

• Look at the oil level and quality. If the oil looks dirty or cloudy, replace it with fresh vacuum pump oil.

If the Issue Continues: Clean the Demister

The demister helps prevent oil mist from escaping the pump. If you still see fog or mist after the above steps, the demister may need cleaning.

How to Clean the Demister:

1. Watch the video guide: How to clean the demister
2. Turn off and unplug your freeze dryer for safety.
3. Remove the demister (usually located near the vacuum pump). Follow the manufacturer’s instructions for removal.
4. Clean the demister with warm, soapy water and a soft cloth or sponge. Avoid anything abrasive. Rinse thoroughly to remove all soap.
5. Let it dry completely before putting it back.
6. Reattach the demister securely.
7. Plug in and test your freeze dryer to make sure everything is working properly.

Need More Help?

If you have concerns or notice the demister is damaged, please contact Harvest Right Support:

• Phone: 801-386-8960
• Submit a support ticket: Harvest Right Helpdesk

We’re here to help!