A single reference document packs exposure limits, incompatibility warnings, respirator guidance and first aid instructions into one compact entry per chemical. The NIOSH Pocket Guide to Chemical Hazards, commonly shortened to the NPG, has served as exactly this kind of practical reference for workers, employers and occupational health professionals for decades. Knowing what actually sits inside each entry makes the guide far more useful than treating it as just another safety data sheet.
What the NPG Is Actually Built For
The NPG delivers general industrial hygiene information covering hundreds of individual chemicals and broader chemical classes, including groupings like cyanides, fluorides and manganese compounds. NIOSH is explicit that the guide presents key facts rather than every relevant detail on a given substance, positioning it as a fast recognition and control tool rather than a comprehensive technical dossier.
Every Entry Follows the Same Structure
Each chemical entry in the NPG follows a consistent format, which is exactly what makes the guide fast to use once you know where to look. A complete entry includes:
Chemical names, synonyms, trade names, along with CAS, RTECS and DOT identification and guide numbers.
Chemical structure, formula and relevant conversion factors.
NIOSH recommended exposure limits, known as RELs.
OSHA permissible exposure limits, known as PELs.
NIOSH's immediately dangerous to life and health values, or IDLHs.
Physical description along with chemical and physical properties of the substance.
Measurement methods used to detect and quantify the chemical.
Personal protection and sanitation recommendations.
Respirator selection guidance.
Incompatibilities and reactivities with other substances.
Exposure routes, symptoms, target organs and first aid information.
That last category deserves particular attention from buyers and facility teams. Knowing a chemical's specific target organs and expected symptoms ahead of time can meaningfully speed up first response in an actual exposure incident.
NIOSH makes the NPG available through three distinct formats, each suited to a different work context. The guide exists as a searchable online version, a downloadable PDF running roughly 6.2 megabytes, and a mobile web app built for Apple and Android phones.
For facility teams needing to check a chemical quickly on a warehouse or plant floor, the mobile version offers the fastest path. For safety officers building formal documentation or training materials, the PDF version provides a stable, citable reference that will not change unexpectedly between checks.
The Indexing System Makes Cross Referencing Easy
Beyond individual chemical entries, the NPG maintains dedicated indices that make cross referencing genuinely simple. A dedicated Index of Chemical Names, Synonyms and Trade Names helps users find a chemical even when they only know a common or brand name rather than its formal chemical designation. A separate Index of CAS Numbers and an Index of RTECS Numbers let users search directly by registry number when that is the identifier available.
This matters for chemical buyers dealing with suppliers who may use different trade names or regional naming conventions for the same underlying substance. Cross checking a CAS number against the NPG index confirms identity regardless of what name appears on a supplier's paperwork.
What to Do When a Chemical Is Not Listed
Not every chemical a facility handles will appear in the NPG, and NIOSH addresses this gap directly rather than leaving users without guidance. For chemicals not listed, or those lacking a formally established occupational exposure limit, NIOSH specifically recommends consulting its Occupational Exposure Banding resource instead, which allows safety professionals to assign an interim hazard category based on available scientific data even without a formal limit in place.
Getting a Physical Copy
CDC's direct ordering service for printed NPG copies has been retired, so anyone wanting a physical copy needs to go through outside vendors instead. Both the Government Publishing Office, through its Superintendent of Documents program, and the National Technical Information Service offer the guide, with the NTIS version available specifically as a PDF download through its order desk.
Practical Ways to Use the NPG in a Trading Workflow
Chemical buyers and safety teams can build a few concrete habits around this resource without needing specialized toxicology training.
Search by CAS number first when checking a new supplier's chemical, since trade names can vary significantly between regions and companies.
Compare the listed REL and PEL values side by side, since NIOSH recommended limits and OSHA legal limits do not always match, and the stricter of the two often deserves more weight in internal safety planning.
Check the incompatibilities and reactivities section before co-storing any new chemical with existing warehouse inventory.
Note the DOT ID and guide number for any chemical requiring transport, since this connects directly to emergency response guidance during shipping incidents.
The Bottom Line for Procurement Teams
The NIOSH Pocket Guide condenses an enormous amount of practical safety information into a format built for fast, real world reference rather than academic study. Its consistent structure across hundreds of chemicals means once a safety team learns how to read one entry, they can navigate any other entry in the guide just as quickly. For chemical buyers handling a wide or changing portfolio of substances, that consistency is exactly what makes the NPG worth checking as a routine step before a new chemical ever enters a facility.
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Reference Link:
https://www.cdc.gov/niosh/npg/default.html
