What chemicals are used in refrigerators

Refrigerators for chemicals

The information given here has been compiled to the best of our knowledge and belief. Hopefully they will help, but unfortunately they cannot guarantee their accuracy or completeness. In particular, they do not release you from independent research and decision-making with regard to the measures to be taken when dealing with hazardous substances. Notes, feedback and questions are welcome.

In the RiSU it says:

Flammable liquids (e.g. diethyl ether, pentane, acetaldehyde) may only be kept in the refrigerator in justified exceptional cases. It must not have any sources of ignition in the interior. Ignition sources in the refrigerator in the normal version are e.g. B. lights, light switches, temperature controllers, automatic defrosting. The converted refrigerators must be marked with the inscription: "Only interior free from ignition sources".

Why is?

A refrigerator fulfills its purpose particularly well when it is absolutely leak-proof. If, however, there is a highly flammable liquid in the refrigerator and the vapor can escape from the container, an evaporated volume of a few milliliters is sufficient in commercially available refrigerators to create an explosive atmosphere in the refrigerator. Serious accidents caused by exploded refrigerators are known from the past.

Its flash point reveals whether a liquid in the refrigerator can create an explosive atmosphere. Since the fire hazard classification also depends on this flash point, the following applies:

  • A liquid that is not marked with the flame pictogram (GHS02) cannot create an explosive atmosphere outside at room temperature or inside the cooled area.
  • For a liquid with the flame pictogram (GHS02) and the H-phrase H226: Flammable liquid and vapor is marked, the same applies. However, if the temperature is low, an explosive vapor / air mixture can arise. Nevertheless, the RiSU demands that such liquids are only allowed to be kept ready in the refrigerator in "justified exceptional cases".
  • A liquid with the flame pictogram (GHS02) and either the H-phrase H225: Highly flammable liquid and vapor or H224: Extremely flammable liquid and vapor is marked can possibly form an explosive atmosphere in the refrigerator.

You will get an exact statement by researching the flash point. The following applies to the liquids named as examples in the RiSU:


substanceFlash point [° C]
Diethyl ether-40

Diethyl ether and pentane can easily create an explosive atmosphere even in the freezer. If the cooling capacity is not set too weak, however, the freezer compartment becomes a safe place to store acetaldehyde - at least as long as the refrigerator is working and not defective or without power. Acetaldehyde has a very low boiling point of 20 ° C. So if it gets a little too warm in your chemistry room or in your collection room, the contents of the bottle come under pressure and are therefore better stored in the refrigerator, especially since liquid aldehydes tend to gradually oxidize to the corresponding carboxylic acid at room temperature, i.e. to spoil!

Ways to a compliant refrigerator

If, for example, a faulty lid that does not close tightly causes an explosive atmosphere to develop inside the refrigerator, there must never be an ignition source inside. That is the reason for the requirements of the RiSU. If you have a "real" laboratory refrigerator, you're fine. But what do you do if nobody wants to finance the necessary € 1,500 to € 3,000 and that's why you stay with a household refrigerator?

  • Temperature controller: There are household refrigerators in which the operating elements (e.g. temperature controller) are located outside the refrigerator compartment. It is not necessary that the control elements are also visible from the outside. They can be hidden by the door and just need to be outside the door seal.
  • Lighting: You will have to take care of the interior lighting yourself. Removing the light source is not enough, the existing electrical system must no longer be in contact with the interior. This is where you will need to be creative. Options are: Mask with a suitable piece of plastic or seal the lamp housing yourself, e.g. with hot glue.
  • Automatic defrosting: The condensate that runs down the inner rear wall usually runs through a small hole to the outside, where it lands on a tray that is heated by the compressor, which should allow the water to evaporate. You have to close this opening. Maybe you are lucky and you can use a hose to divert the condensate into one of the lower vegetable drawers. Otherwise you will have to wipe more often ...
  • For the labeling With the text "Only interior free from ignition sources" there are ready-made solutions.

If you do not succeed in fulfilling the catalog of requirements, you have to attach another sign to your refrigerator (and of course stick to it):

It is forbidden to store flammable substances in this refrigerator!

Pay attention to your powers! You are allowed to remove the light source from a refrigerator, but not to modify the electrical system. It is therefore worthwhile to choose a refrigerator in advance that comes close to the target in the factory condition, i.e., in addition to the operating elements attached to the outside, it also has an easily sealable lighting opening or lighting housing. Of course, it shouldn't have a fan etc. either. Since the companies change their models again and again, you have to look for yourself which models are currently suitable.

Handling the (converted) refrigerator

  • Only place gas-tight containers in the refrigerator. A cork, for example, is not gas-tight.
  • Secure the ground joint with a clamp and protect the round bottom flask from falling over, e.g. by placing it in a beaker.
  • Don't overload the fridge!
  • Defrost iced refrigerators! An icy refrigerator does not cool properly. Don't scratch the ice! If you damage a cooling coil in the process, the refrigerant can suddenly escape, which is flammable and therefore suddenly creates an explosive atmosphere!
  • "Keeping flammable liquids ready" in the refrigerator is rarely justified. (Exception: acetaldehyde, see above) If recrystallization was carried out from a flammable solvent and the crystallization is to be completed by further cooling in the refrigerator, this is not a "standby" in the sense of the RiSU, but rather a use. The setting of the supersaturated solution is also "justified", because this is done for the success of the experiment.
  • Keep the amount of flammable substances as small as possible. In the sense of the RiSU, it is easier to handle if you only put all substances marked with the flame pictogram (GHS02) in the refrigerator if this is objectively required. Incidentally, even non-flammable substances have no business in the refrigerator for no reason, but at least they do not pose any risk of explosion.
  • Label chemicals that are not in the original containers with the originator, content and date so that your colleagues also know what it is and who discontinued it and when.
  • Any contents of the refrigerator that are no longer required must be disposed of.

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