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Facing Your Laboratory Freezer: Dos and Don’ts For Defrosting Day

Facing Your Laboratory Freezer: Dos and Don’ts For Defrosting Day

Your stomach clenches. Sweat snakes down your torso. The world seems to slow down.

You begin the long, terrifying walk down the corridor. Your mind calls out to you to, “Run! Run now!” but you soldier on until you reach the door and knock. There is no escaping the wrath you will evoke when you have to tell your PI that you have just broken the lab’s expensive freezer.

(dramatic pause)

No one should have to go through this! In this article, we’ll go over the dos and PLEASE DON’TS! of cleaning a freezer so you can confidently approach this task knowing you’re not going to end up sobbing to your supervisor!

The Dos

The basic steps to thawing a freezer should work for regular -20°C freezers and also large -80°C models, but you should also consult your freezer’s manual for make/model specific details

Step 1: Before you start

  • Before you start, tell everyone in the lab to go through the unit and remove all unwanted samples.
  • Designate an alternate freezer for temporary storage and tell people to move all the stuff they want to keep to an alternate freezer.
  • Be firm and set a deadline. Let people know that any remaining personal samples will be thrown out!

Step 2: Sleepy time

  • Unplug the freezer and tape the cord off the floor so it doesn’t get wet, stepped upon or tripped over.

Step 3: Digging for treasure

  • Be sure to keep track of where everything is! I like to put everything on an empty shelf in another freezer and then put a sticker/post-it on the outside.
  • Put a post-it by your computer or add a note in your lab book with where you put everything just in case!
  • Let everyone know where the temporary storage is.
  • Remove any shelving or plastic storage areas.

Step 4: Prepare for the floods

  • Leave the door(s) open overnight, or for as long as it takes for all the ice to thaw. Use a bin/prop to hold doors open. For doors that are higher up, I like to use a folded wad of paper towels (or cardboard) jammed between the two door hinges to force the doors to stay open. The towels can be reused later when you’re mopping up the inside of the freezer or cleaning the fridge.
  • Check under and behind the freezer for a pipe that may be the water escape for melted ice. If you can’t find it, and your manual isn’t helpful, continue on to the next points.
  • Place shallow pans, absorbant papers and/or towels under and around the freezer to catch the water. You can purchase special floor mats that absorb water. The blue variety with plastic on the underside or white bench paper are not great here even though they’re the ones you see most commonly in front of fridges and freezers. You can purchase thicker mats that have no plastic and thus can absorb larger amounts of fluids. These are a better option than towels when it’s a lab fridge because they’re disposable. If you have them, newspapers also do the trick well!
  • BEWARE! Different freezers melt in different ways. Usually, the ice thaws and comes out the front as a puddle but some freezers thaw and melt out the back! If you’re not sure, check your manual or prepare for both possibilities. It may be necessary to pull the unit away from the wall.
  • Check on the open freezer regularly. Puddles may get into other machines and cause an electrical fire or someone may slip on them. Put up an obvious sign if possible, to warn others that the floor may to wet.
  • If you have some time and the freezer needs to be back in order quickly you can speed up the process. These include: using a hair dryer; a wet, hot towel, oven mit or sponge ; a fan; or heat a metal spatula in boiling water and press it to the ice. Beware!!!! If you decide to use a hair dryer, beware of getting electrocuted! Water and electricity are not meant to mix. Keep the hairdryer away from ice and water and hold the cord out of the way. Don’t do this while standing in a puddle either!

Step 5: Wipe and dry

  • Once the ice has melted, wipe the insides of the unit down to ensure they’re completely dry. If you leave them wet, the ice will come straight back.
  • Clean the unit if it is dirty. Baking soda and hot water work, or for a more intense clean, use 10% bleach solution.

Step 6: Ready for work

  • Once the unit is completely clean, dry and pushed back into position, plug it in.
  • Monitor the temperature of the freezer and fridge by placing a thermometer inside the unit and adjust the temperature control as necessary.
  • Let everyone know when the unit is working again so they can replace their stuff.

NOTE: if your unit contains radioactive or biohazardous materials or hazardous chemicals add the below steps.

  • Radioactive: Collect some ice, and test it with a liquid scintillation counter. If the melted ice registers greater than 3 times background (compared to tap water control), collect the ice as radioactive waste and label it for pickup according to your lab’s safety procedures and decontaminate the unit as appropriate.
  • Biohazardous: Collect the ice and add 1 part bleach to 9 parts melted ice. After 20 minutes pour into drain, ideally in a fume hood.
  • Chemical: ensure the unit has been carefully wiped down and the paper towels used to clean the unit are disposed of appropriately.

The Don’ts

  • Never use a knife or similar tools to remove ice! They may damage your freezer or even cause a gas leak! Don’t do it! Don’t even think about it!!! No matter how cautious you are, it just isn’t worth the risk. If you want to scrape at the ice, use something blunt and plastic, like a plastic spatula.
  • Don’t add a bunch of unfrozen stuff to the freezer once you’re done or your freezer’s motor may overload. No one likes to come back to a desk full of work after a holiday.
  • Don’t treat a fridge that contained radioactive or biohazardous materials or hazardous chemicals the same way as a normal fridge!

Share your thoughts, funny stories and learnings below!

Happy thawing!

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  1. Katie on November 21, 2018 at 8:07 pm

    Thanks for these helpful practical tips! We plan to defrost ours on Friday. Right now it looks more like a storehouse for small glaciers, than for our reagents and research samples. Hopefully ours doesn’t thaw through the back 🙂

  2. Yani on November 15, 2016 at 1:31 am

    Freezer in my worklab cannot be open because the ice

  3. Marra on March 10, 2016 at 2:57 pm

    Very Informative. i enjoyed reading these helpful hints as i am a new Lab Manager and want to make sure our equipment is working, and cleaned properly.
    Thanks so much for the help 🙂

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