Biosafety Level 1 (BSL-1)

Biosafety Level 1 (BSL-1) is the lowest and least restrictive of the four graded laboratory-containment tiers defined by the CDC/NIH publication Biosafety in Microbiological and Biomedical Laboratories (BMBL, 6th edition, 2020). A protocol is assigned BSL-1 when it involves well-characterized agents that are not known to consistently cause disease in healthy adult humans and pose minimal potential hazard to laboratory personnel and the environment. This page covers what BSL-1 specifically requires; for how BSL-1 relates to BSL-2, BSL-3, and BSL-4, and how a Biosafety Level is formally assigned, see the general Biosafety Level (BSL) entry — that context isn’t repeated here.

What makes a protocol BSL-1

BSL-1 is the baseline containment level in the BMBL’s four-tier system: BSL-2, BSL-3, and BSL-4 each add practices, PPE, and engineering controls on top of it rather than replacing it, so every biosafety practice required at BSL-1 continues to apply at the higher levels too. BSL-1 work is typically performed on the open bench, using standard microbiological practices, without the certified biosafety cabinets, restricted access, or specialized ventilation that higher tiers require. It is most often used for routine teaching and research laboratories, undergraduate and graduate coursework, and basic research with agents that have a long, well-documented safety record and no meaningful capacity to cause disease in a healthy adult under normal laboratory exposure conditions.

Typical agents handled at BSL-1

Agents commonly assigned BSL-1 containment include non-pathogenic, disabled laboratory strains of Escherichia coli (such as the widely used K-12 strain and its derivatives), Bacillus subtilis, and Saccharomyces cerevisiae (baker’s/brewer’s yeast) — organisms that are well-characterized, do not typically infect healthy adults, and are treated as adapted so that they do not survive or colonize efficiently outside a controlled laboratory environment. This is a representative, not exhaustive, list; the actual containment for any specific agent, strain, or vector is determined by an Institutional Biosafety Committee (IBC) risk assessment, not inferred from this list alone — a superficially similar organism (a pathogenic E. coli strain, for instance, rather than a disabled K-12 derivative) can require BSL-2 or higher despite sharing a species name with a BSL-1 agent.

Required practices at BSL-1

BSL-1 establishes the standard microbiological practices that all higher containment levels build on:

• Standard access. The laboratory is not required to be separated from general building traffic patterns, and access is not restricted the way it is at BSL-2 and above.
• Handwashing. Personnel wash their hands after handling viable materials, after removing gloves, and before leaving the laboratory.
• No eating, drinking, smoking, or applying cosmetics in the work area, and food is stored separately from areas where agents are handled.
• Mouth pipetting is prohibited; mechanical pipetting devices are used instead.
• Policies for safe sharps handling, even though BSL-1 work more rarely involves sharps than higher tiers.
• Routine decontamination of work surfaces after any spill and at the end of each work day, and decontamination of laboratory wastes before disposal using an effective method such as autoclaving or chemical disinfection.
• A biosafety or chemical hygiene manual appropriate to the work, followed by laboratory personnel.

Safety equipment and PPE at BSL-1

BSL-1 does not require a certified biosafety cabinet (BSC) for routine work, unlike BSL-2 and above, because BSL-1 agents are not considered a meaningful aerosol-transmission risk to healthy personnel. Primary containment is achieved through standard microbiological technique rather than specialized engineering controls. PPE is correspondingly minimal: a lab coat or gown and, where there is a reasonable expectation of splash or contact, gloves and safety glasses. Special containment devices are generally not required for manipulations of BSL-1 agents.

Facility features required at BSL-1

A BSL-1 laboratory is built to standard, sturdy construction with a door that can be closed, work surfaces that are easily cleaned and impervious to the liquids in use, and a sink for handwashing. Windows that open to the exterior, where present, are fitted with fly screens. Unlike BSL-2 and above, BSL-1 does not require self-closing or lockable doors, a dedicated eyewash station immediately in the room, or on-site decontamination equipment such as an autoclave — a BSL-1 laboratory can rely on decontamination equipment located elsewhere in the building. Furniture is designed to support easy cleaning and be functional for the work performed.

Who assigns BSL-1, and how it’s reviewed

For research involving recombinant or synthetic nucleic acid molecules, the containment level — including BSL-1, when a protocol’s risk assessment supports it — is formally assigned by an institution’s Institutional Biosafety Committee (IBC) under the NIH Guidelines, as part of a protocol registration and risk-assessment process. A meaningful share of well-characterized BSL-1 work (for example, many routine uses of standard E. coli K-12 cloning strains) qualifies for an exempt or simplified registration category under the NIH Guidelines rather than requiring full IBC review at the same depth as higher-risk work, though institutional policy on what qualifies as exempt varies and the IBC retains authority to require full review of any protocol. That process, IBC composition requirements, and how BSL relates to an agent’s underlying Risk Group are covered in full on the general Biosafety Level (BSL) page rather than repeated here.

Worked examples

Example 1. An undergraduate microbiology teaching laboratory has students culture and Gram-stain Bacillus subtilis on the open bench. The course follows standard BSL-1 practice — handwashing before and after the exercise, no food or drink in the lab, decontamination of bench surfaces with a disinfectant at the end of the session, and autoclaving of used culture plates before disposal — without a biosafety cabinet or restricted-access signage, because B. subtilis is a well-characterized, non-pathogenic organism.

Example 2. A molecular biology research lab performs routine plasmid cloning using disabled E. coli K-12 derivative strains. The lab’s Institutional Biosafety Committee has reviewed the general cloning vectors and host strains in use and assigned BSL-1 containment; personnel work on the open bench following standard microbiological technique, and waste containing the bacterial culture is autoclaved before disposal.

Counter-example

A laboratory working with a clinical isolate of pathogenic Escherichia coli (for example, a Shiga toxin–producing strain recovered from a patient sample) is not a BSL-1 example, even though the genus and species name matches a common BSL-1 laboratory strain: because that isolate is known to cause disease in healthy adults, an IBC risk assessment would assign it BSL-2 containment at minimum, requiring a certified biosafety cabinet for aerosol-generating steps, restricted access, and biohazard signage that BSL-1 work does not require. Agent identity at the species level alone doesn’t determine the level; the specific strain’s characterized pathogenicity does.

Related terms

• Biosafety Level (BSL) — the full four-tier system (BSL-1 through BSL-4) and how a level is assigned
• Biosafety Level 2 (BSL-2)
• Biosafety Level 3 (BSL-3)
• Biosafety Level 4 (BSL-4)
• Laboratory Safety (OSHA Chemical Hygiene Plan) — the parallel OSHA framework for chemical, rather than biological, laboratory hazards

For the broader compliance context this term sits within, see the Integrity & Compliance cluster page.