Laboratories for proposed biohazardous materials work are designed to contain these materials.
There are four defined biosafety levels: BSL-1, BSL-2, BSL-3 and BSL-4. The biosafety level is determined from a combination of lab practices and techniques, safety equipment, and laboratory facility.
The CDC/NIH publication Biosafety in Microbiological and Biomedical Laboratories describes the criteria for different biosafety levels in detail.
The NIH publication Guidelines for Research Involving Recombinant or Synthetic Nucleic Acid Molecules describes containment criteria for work with recombinant or synthetic nucleic acids.
For more information on containment please refer to the Biosafety Manual.