Subpart B
Testing must be done in the sequence: oxygen content first, then flammability, then toxicity. This sequencing is required by 1915.12, which helps ensure entrants are not exposed to oxygen-deficient/enriched atmospheres or explosive or toxic atmospheres before other hazards are evaluated.
Spaces that are sealed, recently painted/non‑ventilated, spaces that contain or have contained combustible/flammable liquids or gases, spaces that contain or have contained toxic/corrosive/irritant materials, fumigated spaces, and spaces with materials or residues that can create oxygen‑deficient atmospheres must be inspected and tested by a competent person before initial entry. See 1915.12(a)(1) for the full list and 1915.12(a)(1)(i)–(v).
A space is considered acceptable for entry when oxygen content is at or above 19.5% and below 22.0% by volume; warning labels may be removed when the oxygen content is within that range. See 1915.12(a)(2) and the note on label removal in 1915.12(a)(3).
No—employees may not enter when oxygen is below 19.5% or above 22.0%, except for emergency rescue or short‑duration entry to install ventilation equipment if continuous monitoring is provided and appropriate respiratory and other PPE from Subpart I is used. See 1915.12(a)(3) and the exceptions at 1915.12(a)(3)(i)–(ii).
A competent person must visually inspect the space for combustible/flammable liquids and must test the space prior to employee entry to determine the concentration of flammable vapors and gases. See 1915.12(b)(1) and the subparts 1915.12(b)(1)(i)–(ii).
If flammable vapors or gases are at or above 10 percent of the lower explosive limit (LEL), the space must be labeled "Not Safe for Workers" and "Not Safe for Hot Work," and employees may not enter until ventilation lowers concentrations below 10% LEL. Labels may be removed once concentrations are below 10% LEL. See 1915.12(b)(2) and 1915.12(b)(3).
A short‑duration entry is allowed only for emergency rescue or to install ventilation equipment necessary to start work, and only if there are no ignition sources present, the atmosphere is monitored continuously, atmospheres at or above the upper explosive limit are maintained where applicable, and respiratory and other appropriate PPE from Subpart I are provided. See 1915.12(b)(3)(i)–(iv).
If air concentrations exceed a Subpart Z PEL or are IDLH, the employer must label the space "Not Safe for Workers," ventilate to bring concentrations within the PEL or below IDLH (or, if that cannot be achieved, have a Marine Chemist or CIH retest until the space can be certified), and employees may not enter such a space. See 1915.12(c)(2)–(4). Also consult 1915SubpartZ for PEL details.
A "competent person" as defined in Part 1915 can perform inspections/testing and specify necessary protections; for Subpart B operations the competent person must meet the additional requirements of [1915.7]. OSHA's interpretation confirms that a competent person may use other occupational exposure limits (OELs), such as TLVs, to evaluate hazards and specify protection when no OSHA PEL exists. See the OSHA letter of interpretation on competent persons (April 18, 2016) at https://www.osha.gov/laws-regs/standardinterpretations/2016-04-18 and 1915.12 for the testing requirements.
Employees who enter confined or enclosed spaces must be trained to recognize confined‑space characteristics, anticipate hazards they may face, recognize adverse health effects from exposure, understand physical signs and reactions, know needed PPE, use PPE, and, where necessary, know about barriers for protection. Training must also cover when to exit (employer order, alarm, or perceived danger). See 1915.12(d)(2)–(3).
Training must be provided before the entrant begins the work and whenever operations or duties change that introduce new hazards. Employers must certify that the training occurred; the certification must contain the employee's name, the name of the certifier, and the date(s) of certification and be available for inspection. See 1915.12(d)(4)–(5).
Each in‑house rescue team member must be provided and trained to use the PPE and rescue equipment needed for confined space rescues (including respirators), be trained to perform their rescue duties, and the team must practice skills at least once every 12 months using mannequins and realistic facilities—unless an actual rescue occurred in that year for the same type, which can substitute for a drill. See 1915.12(e)(1)(i)–(iv) and 1915.12(e)(1)(iii).
Yes—at least one person on each rescue team must maintain current certification in basic first aid that includes airway maintenance, bleeding control, circulation maintenance, and CPR. This requirement is in 1915.12(e)(1)(iv), and OSHA's letter on first aid and bleeding control (June 19, 2019) provides additional context about first aid training expectations (https://www.osha.gov/laws-regs/standardinterpretations/2019-06-19).
An employer must inform the outside rescue team of the hazards they may encounter at the employer's facility so the team can be trained and equipped appropriately; the criteria in 1915.12(e)(1) may be used to evaluate outside rescue services. See 1915.12(e)(2).
Each employer must exchange all available information about hazards, safety rules, and emergency procedures concerning those spaces and atmospheres with any other employer whose employees may enter the same spaces. This requirement is in 1915.12(f).
If a space cannot be ventilated to within applicable PELs or remains IDLH for contaminants, a Marine Chemist or CIH must re‑test until the space can be certified "Enter with Restrictions" or "Safe for Workers." See 1915.12(c)(3).
OSHA's April 18, 2016 letter explains that a competent person under Part 1915 must be capable of recognizing and evaluating hazardous atmospheres and specifying necessary protections; for Subpart B operations the competent person must meet additional [1915.7] requirements. That means the employer's competent person can perform the visual inspections and atmospheric testing required by 1915.12 and determine protections even when no OSHA PEL exists (see https://www.osha.gov/laws-regs/standardinterpretations/2016-04-18).
If a space is oxygen‑enriched (above 22.0% by volume), it must be labeled "Not Safe for Workers - Not Safe for Hot Work," and employees may not enter except for emergency rescue or short‑duration ventilation installation under the monitoring and PPE exceptions in 1915.12(a)(3). See also the labeling and ventilation requirements at 1915.12(a)(2).
Yes—while 1915.12(c) requires compliance with Part 1915 Subpart Z PELs or IDLH values, OSHA's competent person guidance (April 18, 2016) explains that when no OSHA PEL exists a competent person may use other reputable OELs (such as ACGIH TLVs) to recognize hazards and specify protections, provided the competent person meets the Part 1915 competency requirements (see https://www.osha.gov/laws-regs/standardinterpretations/2016-04-18).
The exceptions allow entry for emergency rescue or short‑duration ventilation installation only if the atmosphere is monitored continuously and appropriate respiratory protection and other PPE and clothing required by Subpart I are provided. For flammable atmospheres the exception also requires no ignition sources and maintaining atmospheres above the upper explosive limit where specified. See 1915.12(a)(3)(i)–(ii) and 1915.12(b)(3)(i)–(iv).
The employer must prepare a written certification that training required by 1915.12(d)(1)–(4) has been accomplished; the certification must include the employee's name, the certifier's name, and the date(s) of certification, and must be available for inspection by OSHA, the Director, employees, and their representatives as required by 1915.12(d)(5).