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Nitrogen Tanks

Sample Removal
Technician removing a box from a liquid nitrogen freezer. Image by Donald E. Hurlbert, Smithsonian Institution.



The NMNH Biorepository began operations in 2011 and is believed to be the largest museum-based natural history biorepository in existence. Our current capacity exceeds 4.2 million standard 2 ml cryovials, potentially expandable to 5 million cryovials. Researchers at the National Museum of Natural History (NMNH) have collected material for projects in biodiversity, phylogenetics, population genetics, toxicology, environmental monitoring, etc., since the early 1970s. The recent explosion of genomic science has increased the value of these materials and the rate of genomic collection growth. Centralization of genomic collections began in 2006, and will continue for several years until all archival genomic collections are moved to the Biorepository. We encourage researchers interested in free, permanent, archival storage of DNAs, tissues and phenotype vouchers of genomic research and collections to contact us at (see also "Genomics Research Support" below).



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Collection Storage Facility

Biorepository Freezers
Mechanical freezers in the Biorepository. Image by Donald E. Hurlbert, Smithsonian Institution.

There are two main types of freezers in use at the Biorepository: mechanical and liquid nitrogen. Mechanical freezers are the mainstay for storage of frozen collections and are found in most laboratory facilities. These freezers use a "cascade refrigeration system", which employ two different refrigerants with different boiling points. Our mechanical freezers are special in that they use water to cool the compressors, unlike most freezers that use ambient air to cool the compressors. Thus, there is a reduced need for air conditioning, which makes the facility "greener". Liquid nitrogen freezers work on a different principle: material is stored in a large rotating rack above a pool of boiling liquid nitrogen. This is much like a home vegetable steamer, except that in the case of liquid nitrogen, the boiling liquid is -196°C (-321°F) and the "steam" (actually vapor) is a few degrees warmer.


    The collection storage areas of the Biorepository contain:

    Liquid Nitrogen Freezers
    Liquid nitrogen freezers in the Biorepository. Image by Donald E. Hurlbert, Smithsonian Institution.
  • 16 liquid nitrogen freezers (-190°C/-310°F)
  • 4 liquid nitrogen freezers (-150°C/-238°F)
  • 16 mechanical chest freezers (-80°C/-112°F)
  • 26 mechanical upright freezers (-80°C/-112°F)
  • 15 mechanical upright freezers (-30°C/-22°F)
  • 1 mechanical upright refrigerator (4°C/39.2°F)

    In addition, there are freezers and a refrigerator for temporary storage of collections being processed in the Biorepository Workroom:

  • 1 mechanical upright freezer (-80°C/-112°F)
  • 2 mechanical upright freezers (-20°C/-4°F)
  • 1 mechanical upright refrigerator (4°C/39.2°F)
  • 1 mechanical walk-in freezer (-20°C/-4°F)

All freezers and refrigerators in the Biorepository are continuously monitored by an electronic system that calls responders during an outage or other emergency. This monitoring system is also accessible via a secure web application, so freezer temperatures can be checked remotely at will.

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Cryovials containing tissue. Image by Azhar A. Husain, Smithsonian Institution.

Genomics Research Support


The Biorepository provides material for genomics and other non-commercial research endeavors. These materials can be obtained by first contacting the pertinent NMNH Science Department The Biorepository is also very interested in preserving voucher material, tissue and DNA from organisms used in genomic studies. If you would like to donate these vouchers, please read the following instructions and policies: NMNH Biorepository Standards and Services, Deed of Gift and the NMNH Collections Management Policy. We are happy to answer any questions/concerns you may have. Please send an e-mail to and we will promptly respond.

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