No OSHA standard contains the words "bump test." Several standards require the atmosphere to be tested with a direct-reading instrument, and one of them says the instrument must be calibrated, but none says how often a portable gas detector has to be checked against gas. The answer OSHA gives is in a Safety and Health Information Bulletin, "Calibrating and Testing Direct-Reading Monitors," reissued on November 26, 2024 in place of its 2013 bulletin on portable gas monitors. It adopts the position of the instrument makers' association: a bump test or calibration check before each day's use. This article sets out which standards call for a gas monitor, what the bulletin recommends, the difference between a bump test, a calibration check and a full calibration, what happens when an instrument fails, and what a daily log should cover.
A note on scope: this summarizes federal OSHA standards for general industry and OSHA's published guidance. The bulletin says it is not a standard or regulation and creates no new legal obligations. States with their own OSHA-approved plans can set different rules, and nothing here is legal advice.
The bulletin names three standards that require gas monitors, and the wording of each matters.
Permit-required confined spaces. Under 29 CFR 1910.146(c)(5)(ii)(C), before an employee enters a space under the alternate entry procedures, the internal atmosphere "shall be tested, with a calibrated direct-reading instrument, for oxygen content, for flammable gases and vapors, and for potential toxic air contaminants, in that order," and any employee who enters, or their authorized representative, must be given the opportunity to observe the testing. For full permit entries, 1910.146(d)(5) requires conditions to be tested before entry is authorized and, where the space cannot be isolated because it is large or part of a continuous system such as a sewer, monitored continuously where entrants are working.
Hazardous waste operations and grain handling. 1910.120(c)(6)(ii) requires, during initial site entry where IDLH conditions are possible, "monitoring the air with appropriate direct reading test equipment (i.e., combustible gas meters, detector tubes)," and section 5 of Appendix A to 1910.272 says toxic levels in bins, silos and tanks should be monitored periodically with direct-reading instruments.
The word to notice in the confined space rule is "calibrated." The standard does not define it or give an interval; the bulletin is OSHA's account of what keeps an instrument in that state.
The bulletin's starting point is that workers "must not rely solely on their sense of smell" to warn them of toxic gas, oxygen deficiency or a combustible atmosphere. An instrument that has drifted "can still measure the quantity of gas present, but it cannot convert this information into an accurate numerical reading," and the consequence of a wrong reading is exposure, fire or explosion.
Its central recommendation comes from the International Safety Equipment Association (ISEA), whose 2010 position statement it quotes: "A bump test . . . or calibration check of portable gas monitors should be conducted before each day's use in accordance with the manufacturer's instructions." ISEA recommends, at a minimum, verifying the operational capability of these instruments before each day's use, with additional testing as necessary. The bulletin also recommends standard procedures for calibrating and using monitors that include documentation, and calibration records kept for the life of each instrument.
The bulletin separates three procedures that are often confused on the shop floor.
The sequence the bulletin sets out is short. Before each day's use, a bump test or a calibration check, following the manufacturer's instructions. If the instrument fails either one, a full calibration before it is used. If it fails the full calibration, the employer should remove it from service and contact the manufacturer for assistance or service.
That answers the question most sites ask, which is whether a daily bump test is enough. Under the bulletin it is, provided the instrument passes and the manufacturer's own calibration interval is also kept, since the daily check is done "in accordance with the manufacturer's instructions."
Calibration drift "happens to all sensors over time," the bulletin says, and it lists what speeds it up: normal chemical degradation of sensors and drift in electronics, use in extreme temperature, humidity or dust, exposure to high concentrations of the target gases, exposure of catalytic LEL sensors to volatile silicones, hydride gases, halogenated hydrocarbons and sulfide gases, exposure of electrochemical toxic sensors to solvent vapors and corrosive gases, and the shock and vibration of handling.
Operators should validate a monitor's operability when any of these conditions occurs or is suspected during use, not only at the start of the day, because a monitor that looks undamaged "could be damaged internally." A sensor that will not calibrate is replaced or sent to qualified service.
The calibration interval. The bulletin fixes the daily check and defers the full calibration schedule to the manufacturer. The due date on each instrument is yours to track.
The record. The bulletin recommends records for the life of each instrument, so that one "that has a history of excessive maintenance/repair, or is prone to erratic readings" can be identified and sensor drift tracked to decide when sensors need replacement. It prescribes no format.
The gases. Which sensors a monitor needs depends on the hazards of the space and the task. The confined space standard fixes the order of testing, oxygen first, then flammables, then toxics; the safety data sheets and the permit decide the rest.
Our portable gas detector bump test log, free as a PDF, Excel or Word file, is built around the bulletin's daily check.
Detector:
Bump test:
Result:
If your procedure uses a calibration check rather than a bump test, add a reading for each sensor against the cylinder concentration and the manufacturer's tolerance.
The bulletin's path is a full calibration before use, and removal from service if that fails, so the log should make the outcome unavoidable: a failed result tags the instrument out, assigns the calibration or the service to someone, and the task that needed the detector waits for a spare that has passed its own check that day. What happens to the entry or the shift that depended on it is a site decision, better made before the day the instrument fails.
Bump test programs fail in familiar ways: the clipboard log shows the same initials every morning, the test gas expired last quarter, and nobody can say which instrument was in the confined space on the day it mattered.
For the permits that depend on these readings, see designing a digital permit-to-work and lockout process, and for the same approach applied to the other daily and weekly safety checks, safety inspections that get done.
If your sites run daily bump tests alongside confined space entries and other safety rounds, see how Vardian handles safety inspections and corrective action: checkpoint scans on each instrument, each sensor's result captured as the gas is applied, and failures that become work orders.
Bring a round, an inspection or a maintenance process to a demo, and we'll show how it runs in Vardian.
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