The Definition of NIOSH

Definition of NIOSH

NIOSH, the National Institute for Occupational Safety and Health, is the U.S. federal agency responsible for research and recommendations to prevent work-related injury, illness and death. It was created by the Occupational Safety and Health Act of 1970, the same law that created OSHA, and is part of the Centers for Disease Control and Prevention (CDC) within the Department of Health and Human Services.

NIOSH and OSHA have different roles. OSHA, part of the Department of Labor, sets and enforces legally binding workplace safety standards and can issue citations. NIOSH does not enforce rules or issue fines. Instead, it studies workplace hazards, develops recommendations, trains professionals and provides the scientific evidence that OSHA and other agencies often use when writing regulations.

For safety professionals, NIOSH is one of the most important sources of free, research-based guidance on chemical exposures, noise, ergonomics, respiratory protection, fatigue and many other hazards.

What NIOSH Does

Recommended exposure limits

NIOSH publishes recommended exposure limits (RELs) for hundreds of chemicals and physical agents. RELs are not legally enforceable, but they are often more protective than OSHA's permissible exposure limits because many OSHA limits date from the early 1970s. NIOSH also publishes values for concentrations that are immediately dangerous to life or health (IDLH). See occupational exposure limit (OEL).

Respirator certification

NIOSH tests and approves respirators used in U.S. workplaces under 42 CFR Part 84. OSHA requires employers to use NIOSH-approved respirators, such as the N95 respirator, as part of a respiratory protection program. NIOSH also tracks counterfeit and misrepresented respirators.

Health Hazard Evaluations

Employers, employees and union representatives can request a free Health Hazard Evaluation, in which NIOSH investigators visit a workplace to assess possible health hazards and recommend ways to reduce them.

Fatality investigations

Through its Fatality Assessment and Control Evaluation (FACE) program and related work, NIOSH investigates selected workplace deaths and publishes reports describing what happened and how similar deaths can be prevented. These reports are widely used in training.

Guidance and tools

• The NIOSH Pocket Guide to Chemical Hazards, a quick reference on exposure limits, properties and PPE for common chemicals.
• The NIOSH Lifting Equation for evaluating manual lifting tasks.
• The widely used hierarchy of controls graphic.
• Guidance on noise, including a recommended noise limit of 85 dBA over an 8-hour shift. See noise-induced hearing loss.
• The Total Worker Health program, which connects safety with broader worker well-being.

Training and research funding

NIOSH funds university Education and Research Centers that train industrial hygienists, occupational health nurses, safety engineers and physicians, as well as research programs across agriculture, construction, mining, healthcare and other sectors.

How Employers Can Use NIOSH Resources

• Compare OSHA limits with NIOSH RELs and aim for the more protective value when setting internal exposure targets.
• Check that every respirator in use carries a valid NIOSH approval.
• Use NIOSH fatality reports and hazard alerts in toolbox talks and training.
• Use NIOSH guidance as a starting point for industrial hygiene assessments.
• Request a Health Hazard Evaluation when the cause of a health problem is unclear.

Example of NIOSH

Workers at a commercial bakery began reporting coughing, wheezing and nasal symptoms. The company's own air sampling showed flour dust levels below the OSHA limit for general dust, so managers were unsure what to do. The safety manager requested a NIOSH Health Hazard Evaluation.

NIOSH investigators surveyed workers, sampled the air and reviewed medical records. They found symptoms consistent with flour-related occupational asthma and recommended local exhaust ventilation at mixers, changing how flour was added to reduce dust clouds, medical surveillance and respiratory protection during cleaning tasks. The company put the recommendations in place and used the report to set internal exposure targets.

Frequently Asked Questions: NIOSH

What is the difference between NIOSH and OSHA?

OSHA sets and enforces legal workplace safety standards. NIOSH conducts research and makes recommendations but does not enforce rules or issue penalties.

Are NIOSH exposure limits legally required?

No. NIOSH RELs are recommendations. However, they are often more protective than OSHA limits, and many employers use them as best practice.

What does NIOSH-approved mean on a respirator?

It means the respirator model has been tested and certified by NIOSH to meet federal performance standards. Approved respirators show a NIOSH approval number on the device or packaging.