When buying a laboratory use freezer or refrigerator, there are several things that need to be taken into consideration.  These factors can help you determine not only the most effecient model for your application, but also address any safety concerns you may have.  As always, safety comes first in the lab. 

1.  Consider what you are storing:  You can store biological samples in a freezer that you would not dare use for volitile organic solvents!  Some common application specific types include flammable material storage, explosion-proof, chromatography, blood bank, Ultra Low Temperature (ULT), Cryogenic, and blood plasma models. 

2. Consider Size:   How much storage space do you need?  Will an undercounter unit do, or do you need a 75 cubic foot monster?  Don't forget to also consider the placement of the unit, and if it will fit in the intended space. 

3. Consider Safety Features:  Do you work with very temperature sensitive samples?  Perhaps you could use a temperature alarm to let you know when your work is in danger.  Many of these come standard on ULT's, Blood Bank, and Cryogenic units.  Common features include the following.

Temperature Alarm: Alerts you to over/under temperature (and possibly extreme ambient) conditions.  May be visual, audible or both. 

Temperature Chart Recorder: Provides a temperature over time visualization of your unit.

Keyed Lock:  Keeps your work safe!

Backup Battery System:  Makes sure your work is safe during outages.

Surge/Brown Out Protection Systems:  Keeps voltage at a manageable level, as to safeguard electronics and keep your unit functioning

Microprocessor Control:  Allows greater precision in temperature control and consistency.

4. Consider Voltage:  Be sure to note the type of plug the unit will be using.  Also to take into consideration, the voltage used.  U.S. appliances use  110 to 120 volt, 60 Hz power. 

5. Consider Temperature:  How cold is too cold?  Most specialty models will adhere to an approximate temperature range due to the specifics of the application.  Some common ranges:

Flammable Materials, Explosion Proof, General Purpose:  Refrigerator: 0 to 10 C (32 to 50 F),  Freezer: approximately -30 to 0 C (-22 to 32 F)

Ultra Low Temperature Freezers (ULT's): -40 to -86 C (-40 to -122 F)

Cryogenic Freezers:  down to -125 C (-193 F)

Don't be afraid to ask questions!  It is better to ask now then try to ship it back later.