P&IDs are one item in the equipment process safety information required by 29 CFR 1910.119(d)(3)(i)(B), alongside materials of construction, electrical classification, relief system design and design basis, ventilation design, design codes and standards employed, material and energy balances, and safety systems. The standard requires PSI to be updated whenever a change requires it, under the MOC provision (l)(4), and requires the employer to document that equipment complies with RAGAGEP under (d)(3)(ii). OSHA has not issued a letter specifically on P&ID accuracy, but its letters on equipment PSI show what "documented" means in practice.

What OSHA Has Said

Dec 22, 2003
Design basis documentation must include codes, assumptions, and calculations
A pipeline company asked how to document the design basis for building ventilation under (d)(3)(i)(E). OSHA said the PSI must include the design basis, the codes and standards employed under (d)(3)(i)(F), and all assumptions and calculations. Industry standards such as NFPA 30, NFPA 58, and IIAR Bulletin 111 can serve as the design basis. OSHA also pointed out that API 500 does not allow ventilation to reclassify an enclosed area handling hydrocarbons as unclassified, so documentation claiming that would violate (d)(3)(ii). A company's own standard qualifies only if it reflects recognized and generally accepted good engineering practice.
Read OSHA Letter ↗
Mar 5, 1998
Equipment built to older code editions
An engineering firm asked about vessels built to the 1972 edition of ASME Section VIII. OSHA said an older edition counts as a code "no longer in general use" under (d)(3)(iii). The employer must determine and document that the equipment is designed, maintained, inspected, tested, and operated safely, and that determination becomes the baseline for future inspection and maintenance. Recalculation isn't required where the original design is consistent with current editions, but differences must be documented and justified. Where no records exist for materials, welding, or radiography, it is appropriate to assume the lowest values in the engineering analysis.
Read OSHA Letter ↗
Jan 30, 2001
The older-code determination is a one-time baseline
OSHA clarified that the (d)(3)(iii) determination for existing equipment built to codes no longer in use is a one-time baseline made before the original PHA or startup. Employers don't have to redo it every time a code is revised; mechanical integrity, MOC, PHA revalidation, and PSSR handle ongoing changes.
Read OSHA Letter ↗
Jul 12, 2006
Changes and replacement parts belong in the PSI
OSHA said MOCs for chemicals or equipment become part of process safety information and must be kept for the life of the process, and that equipment PSI must cover all component parts, whether original or replacement, even when a replacement in kind needed no MOC.
Read OSHA Letter ↗

⚡ Key Compliance Takeaway

Treat P&IDs and the rest of your equipment PSI as live documents: every MOC that changes equipment, piping, or controls should close only after the drawings and design basis are updated. Keep the codes, assumptions, and calculations behind each design, not just the result. For older equipment, keep the documented baseline that shows it is still safe to operate.