OSHA 29 CFR 1910.151(b) requires only that "adequate first aid supplies shall be readily available" in the absence of a nearby infirmary, and OSHA has never adopted ANSI Z308.1 as a binding rule, per its 2002-04-18 interpretation letter [S1].
ANSI/ISEA Z308.1-2021, approved on 2022-04-15 and effective from 2022-10-15, is the sixth revision of the voluntary consensus workplace first aid kit standard first issued in 1978; it defines two kit classes (A, B) and four container types (I, II, III, IV) with explicit minimum fill quantities per kit [S2][S3].
What 29 CFR 1910.151(b) actually requires
29 CFR 1910.151(b) is performance-oriented: it names no specific items, no minimum piece counts, and no container type, only that supplies be "readily available" and that a trained first aid person be on site when no infirmary, clinic, or hospital is in near proximity [S1][S4].
OSHA explicitly answers in the 2002-04-18 letter that "ANSI standards become mandatory OSHA standards only when, and if, they are adopted by OSHA; ANSI Z308.1 was not adopted by OSHA," and the agency refers employers to the standard only as guidance in non-mandatory Appendix A to 1910.151 [S1][S3].
The phrase "readily available" is not defined in the rule, but OSHA's interpretation states that the first aid provider "should not have to travel through several doorways, hallways and/or stairways to access first aid supplies," placing the burden of placement on the employer's hazard assessment [S1].
Class A vs Class B: decision matrix
Class A kits are sized for the most common workplace injuries: minor burns, cuts, abrasions, and eye injuries, in low-to-moderate hazard environments such as offices, warehouses, and light assembly, per the ANSI/ISEA Z308.1-2021 fill list [S2][S5].
Class B kits are the higher-quantity, higher-hazard variant, designed for environments with elevated risk of severe injury (for example, manufacturing, construction, fabrication, chemical handling) and must include all Class A items plus a tourniquet and additional trauma dressings [S2][S3].
Container Types I through IV specify mounting and portability: Type I is a stationary indoor cabinet (no portable handle), Type II is portable with a handle for indoor use, Type III is wall-mountable with a door and handle, and Type IV is portable for indoor/outdoor use with a water-resistant case [S2][S6].
Minimum fill quantities that go beyond OSHA
ANSI/ISEA Z308.1-2021 specifies a minimum quantity per kit item; a 25-person Class A kit example lists 79 pieces including 1 oz eyewash, a 5x6 in cold compress, a 4x4 in burn dressing, 3x3 in gauze pads, eye pads with tape, vinyl gloves, BZK antiseptic wipes, and a first aid guide [S5].
The 2021 revision also introduced and emphasized an ongoing maintenance program, an employer-led workplace hazard assessment, formalized quantity and location rules, over-the-counter medication guidance, and separate Bleeding Control Kit provisions as supplementary items, per the Cintas summary of what the revision changed [S3].
Because OSHA's rule contains no count requirement, a one-bandage box could technically be argued as "adequate" for a one-person office; ANSI-compliant Class A and Class B kits close that gap by hard-coding the minimum quantities, which is the practical reason most US distributors label kits as "OSHA & ANSI compliant" [S4][S5].
Who this is for, and who can skip it
For small low-hazard offices (under 25 employees, no machinery, no chemical exposure), a single Type II or Type III Class A kit positioned per the "no multi-doorway" rule typically satisfies both 1910.151(b) and the de-facto industry expectation, and matches what OSHA described in the 2002 letter as adequate for a "small worksite" [S1][S2].
For larger or multi-employer sites, ANSI-compliant Class B kits plus supplemental Bleeding Control Kits are the conservative specification, and ANSI compliance does not exempt the employer from conducting a written hazard assessment and selecting trained first aid responders [S3][S4].
Class A and Class B kits are not appropriate substitutes for industry-specific OSHA rules such as 29 CFR 1910.1030 (bloodborne pathogens) or 29 CFR 1910.151(c) (eyewash, where corrosive chemicals are present); a compliant first aid kit does not by itself satisfy those adjacent standards [S4].
Limits, failure modes, and the "near proximity" trap
OSHA's 2002 letter redirects the "near proximity" question (the historical 3-4 minute and 15 minute EMS response benchmarks) to a later 2007-01-16 policy letter; using ANSI Z308.1 alone to determine kit quantity and location is not a substitute for that proximity-based assessment [S1].
Common audit failures include expired components (BZK wipes, sterile gauze, eyewash), a missing written hazard assessment, kit placement locked inside supervisor offices, and single-source kits in multi-tenant facilities where the "no several-doorway" rule is violated; OSHA inspectors do not have to cite a missing ANSI item, but they can cite 1910.151(b) for inadequate supplies [S1][S4].
For engineering, procurement, and EHS teams specifying kits in 2026, the cleanest defensible path is: pick Class A or Class B by hazard tier, choose Type I-IV by mounting and portability, document the hazard assessment and proximity analysis, and run a recurring expiration check; ANSI Z308.1-2021 remains voluntary but is the de-facto evidence-of-adequacy cited in 1910.151 Appendix A [S1][S2][S3][S7].
Trackable signals for the next review cycle: monitor the ISEA First Aid Standards page for any Z308.1-2026 errata or revision notes, and re-baseline kit contents whenever ISEA publishes a new fill-list infographic [S7].
Spec-level background on the components involved: first aid kit, dye penetrant kit, and pressure transmitter.
Background reading: Triplex vs Quintuplex Plunger Pump: Spec Decision Guide.