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A liquid nitrogen freezer is a cold-storage unit that holds biological material at cryogenic temperatures by using liquid nitrogen (LN2) as the refrigerant, rather than mechanical refrigeration. Samples sit in the liquid itself or in the cold vapor above it, which keeps them far colder than a mechanical freezer can. Typical users are cell-culture and biobank laboratories, core facilities and clinical or research repositories that keep cell lines, tissue and other material for years.
The useful decisions are which freezer class matches the storage job, how the unit is built, and what the capacity and evaporation figures on a data sheet actually describe. The figures below come from manufacturer data sheets and manuals.
What a liquid nitrogen freezer is
It is an insulated vessel that holds liquid nitrogen and the racks, canisters or boxes of sample vials. Cooling comes from the nitrogen. The Lab Manager article by an upright-freezer vendor draws this contrast: mechanical upright freezers give easier access but are vulnerable to power loss and slow to recover after door openings, while tank-style LN2 freezers are more reliable and colder but are loaded from the top.
“Degrees C freezer” searches (for example “deg c freezer” or “celsius freezers”) usually name a temperature class. The ranges for liquid nitrogen storage are roughly -135 C to -196 C in the vapor phase of a tank, and about -196 C in the liquid (see the liquid and vapor phase section).
How it is built
The Phasetwo CCF Series user manual describes a cryogenic freezer as a double-walled, vacuum-insulated container made of aluminum with a fiberglass composite neck tube. The Thermo Scientific CryoPlus 7402 data sheet describes a vacuum-insulated stainless steel chamber with a remote alarm, a 24-LED level monitor and automatic fill with high and low setpoints. Build details from the Phasetwo manual that affect day-to-day care:
- Use liquid nitrogen only; liquid oxygen is not compatible with the unit.
- The liquid nitrogen level should always be below the bottom of the neck tube. Overfilling may cause vacuum loss.
- Scratches in the neck tube area, tampering with the vacuum port, or spilling LN2 on the vacuum port cause vacuum failure.
- Level is measured with a plastic measuring rod (frost line, U-shaped), never with a hollow tube.
- Level and temperature monitoring with a low-level and temperature alarm is recommended.
Liquid phase vs vapor phase
Samples can be kept in the liquid or in the vapor above it. The Thermo CryoPlus 7402 data sheet gives a vapor-phase temperature of -135 C to -196 C. A gas supplier’s explainer (West Air Gases) puts the liquid at a consistent -196 C and describes a temperature gradient in the vapor, so the most critical items are placed lower, and says vapor storage lowers the cross-contamination risk. Tube-level handling is covered in the cryovial guide, and the protocol side in cryopreservation of cells. Temperatures in more detail: liquid nitrogen temperature.
Types and variants
| Type | Typical use | Key difference (source) |
|---|---|---|
| Tank or canister-style LN2 freezer | Long-term storage of vials in racks or canisters | Vapor phase -135 C to -196 C; samples accessed from the top (Thermo data sheet; Lab Manager) |
| Upright LN2 freezer | Frequent-access cold storage without mechanical refrigeration | Set points of -90 C or -150 C, plus or minus 3 C regulation, second thermocouple, 72 h onboard battery; vendor states return to -80 C in under 15 minutes after a 2-minute door opening (Lab Manager, Cryometrix) |
| Mechanical upright freezer | Easier access storage | Easier access but vulnerable to power loss and slow recovery after door openings (Lab Manager) |
For the mechanical ultra-low class, see how to choose an ultra-low temperature freezer.
Sizes and specifications that matter
| Model | LN2 capacity | Storage | Other stated figures |
|---|---|---|---|
| Thermo Scientific CryoPlus 7402 | 200 L | Up to 13,500 2 mL vials | 34 x 28.5 x 41 in |
| Phasetwo CCF35H | 35 L | 10 canisters (2.64 x 11 in) | Neck opening 4.7 in (119 mm); evaporation 0.27 L/day |
| Phasetwo CCF35V | 35 L | 6 canisters (3.7 x 11 in) | Neck opening 4.7 in (119 mm); evaporation 0.27 L/day |
The Phasetwo manual labels evaporation and static hold figures as nominal, so treat them as a model’s rating rather than a measured value for a particular unit. Capacity figures in vials depend on the vial and rack format, which is why the same 35 L class lists 10 canisters in one model and 6 in the other.
Safe use and handling basics
The Phasetwo manual warns that venting nitrogen vapor may deplete oxygen in the air, possibly leading to asphyxiation or death. It says not to use the unit in small, enclosed or poorly ventilated areas and recommends oxygen monitoring. It also carries a frostbite warning and advises seeking medical attention for frostbite. Hazards, PPE and room controls are covered in liquid nitrogen and cryogen handling safety.
Common mistakes
- Filling above the bottom of the neck tube, which the manual says may cause vacuum loss.
- Dipping a hollow tube to read level, when the manual specifies a plastic measuring rod.
- Scratching the neck tube area or spilling LN2 on the vacuum port.
- Installing the unit in a small or poorly ventilated room.
- Running without level and temperature alarms.
FAQ
What temperature does a liquid nitrogen freezer hold?
The Thermo CryoPlus 7402 data sheet gives a vapor-phase range of -135 C to -196 C. Liquid nitrogen itself is about -196 C.
Does a liquid nitrogen freezer need electricity?
Cooling comes from the liquid nitrogen rather than mechanical refrigeration, though the controller, alarms and auto-fill need power. The upright model in the Lab Manager piece adds a 72 h onboard battery, and the 7402 lists a remote alarm, level monitor and auto-fill.
How do I keep track of what is inside?
See lab freezer inventory systems.
Sources
- Thermo Scientific CryoPlus Model 7402 200L Storage System, Technical Data Sheet (checked 2026-10-29): Thermo Fisher Scientific
- Phasetwo Cryogenic Canister Freezer CCF Series User Manual (checked 2026-10-29): user manual PDF
- Lab Manager, “How an Upright Liquid Nitrogen Freezer Works”, vendor-written by Cryometrix (checked 2026-10-29): Lab Manager
- West Air Gases, “How a liquid nitrogen freezer works”, gas supplier (checked 2026-10-29): West Air Gases
