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Atmospheric Testing Log Generator

An entry permit has four blank lines for atmospheric results. A real entry produces dozens of readings — pre-entry, after ventilation, then every time somebody checks. This log records all of them in the order 29 CFR 1910.146(d)(5)(iii) requires: oxygen first, then combustible gases and vapors, then toxics. Enter your acceptable entry conditions once and every row is flagged against them as you type. Print it or save it as a PDF, and staple it to the permit.

If you filled in the confined space entry permit in this browser, this copies the space, the job and the acceptable entry conditions across. Nothing leaves your device.
On construction work 1926.1204(e)(2) requires continuous monitoring unless you can demonstrate that continuous equipment is not commercially available for that hazard, or that periodic monitoring is frequent enough.
OSHA sets no interval. The sample permit in 1910.146 App. D-2 records continuous monitoring results every 2 hours.

Nothing you type is sent to our servers. A draft is kept in this browser until you clear it.

Template for informational purposes only. This document must be reviewed and adapted by a competent or qualified person for your specific jobsite, equipment, and applicable federal, state, and local requirements. It does not constitute legal, engineering, or safety advice and does not by itself establish compliance with OSHA or any other standard. SteelToeTools assumes no liability for its use. Nothing you type is sent to our servers.

How to use this log

  1. 1
    Start from the permit. If you built the confined space entry permit in this browser, the button at the top of step 1 copies the space, the job and the acceptable entry conditions across. The permit authorizes the entry; this log carries the measurements the permit has four lines for.
  2. 2
    Write the instrument down before the first reading. Make, model, serial, last calibration, bump test, and the manufacturer's minimum response time. A log without the instrument on it proves that somebody wrote numbers, not that anybody measured.
  3. 3
    Set the acceptable entry conditions once. Every row you fill in afterwards is compared against them and printed OK or PROHIBITED. Leave a limit blank and that gas prints without a verdict — the log will not invent a threshold.
  4. 4
    Print it blank for the clipboard. Leave the reading rows empty and the sheet comes out ruled, ready for a pen at the portal. The column order is the test order, so the form itself keeps you honest.
  5. 5
    Record the bad reading, not just the good ones. Section 5 exists for the reading that emptied the space: what it was, how the atmosphere got that way, and what was done before anyone went back in. That is the sequence 1910.146(c)(5)(ii)(G) sets out, and the one an investigator asks about.
  6. 6
    Staple it to the permit and keep both. Cancelled permits are kept at least one year for the annual program review — 1910.146(e)(6) and 1926.1205(f). The log is what makes that review worth doing.

What OSHA requires

No standard requires a document called an atmospheric testing log. What the standards require is the testing, and then they require the results to appear somewhere: 29 CFR 1910.146(f)(10) says the permit must carry the results of initial and periodic tests accompanied by the names or initials of the testers and by an indication of when the tests were performed, and 1926.1206(k) says the same for construction. On a real entry that is more data than a permit has room for, which is why the log exists.

The order of tests, and why it is that order

1910.146(d)(5)(iii) is one sentence: when testing for atmospheric hazards, test first for oxygen, then for combustible gases and vapors, and then for toxic gases and vapors. 1926.1204(e)(3) repeats it word for word. Appendix B(5) to 1910.146 explains the reasoning, and it is worth knowing rather than memorizing:

The order of atmospheric tests — 29 CFR 1910.146(d)(5)(iii) and App. B(5)
OrderWhat you testWhy it comes there
1stOxygenMost combustible gas meters are oxygen dependent and will not give a reliable reading in an oxygen-deficient atmosphere
2ndCombustible gases and vaporsThe threat of fire or explosion is both more immediate and, in most cases, more life threatening than toxic exposure
3rdToxic gases and vaporsPerformed last, if tests for toxics are necessary at all

What counts as a hazardous atmosphere

1910.146(b) defines it by five causes. Any one of them is enough:

  • A flammable gas, vapor or mist in excess of 10 percent of its lower flammable limit.
  • Airborne combustible dust at or above its LFL — which the standard says may be approximated as a condition in which the dust obscures vision at 5 feet or less.
  • An oxygen concentration below 19.5 percent or above 23.5 percent.
  • Any substance at a concentration above the dose or permissible exposure limit published in subpart G or subpart Z of part 1910.
  • Any other atmospheric condition that is immediately dangerous to life or health.

Those are floors, not targets. The acceptable entry conditions for a particular space are set by the entry supervisor under 1910.146(f)(9) and are often tighter, which is why every limit on this page is a field rather than a constant.

Two things people get wrong about the readings

A reading at the rim describes the rim. Appendix B(4) to 1910.146: when monitoring an entry that involves a descent into an atmosphere that may be stratified, test the atmospheric envelope about 4 feet in the direction of travel and to each side, and if a sampling probe is used, slow the entrant's rate of progress to accommodate the sampling speed and detector response. Heavier-than-air gases pool at the bottom; methane collects at the top.

The second one is time. Appendix B(3) requires the measurement of each atmospheric parameter to be made for at least the minimum response time of the instrument specified by the manufacturer. Pull a sample through ten feet of tubing and that response time grows; a two-second glance at the display reads the air in the hose.

Continuous or periodic?

In general industry, 1910.146(d)(5)(ii) is a performance requirement: test or monitor as necessary to determine whether acceptable entry conditions are being maintained. Construction is stricter. 1926.1204(e)(2) requires continuous monitoring of atmospheric hazards unless the employer can demonstrate that continuous monitoring equipment is not commercially available for that hazard, or that periodic monitoring is of sufficient frequency to keep it controlled. 1926.1204(e)(1)(iii) adds an early-warning system that continuously monitors for non-isolated engulfment hazards and alerts entrants and attendants in time to get out, and 1926.1206(e) requires the permit to state the means of detecting an increase in atmospheric hazard levels if the ventilation system stops working.

There is no purge time on this page, on purpose

1910.146 sets no ventilation flow rate, no number of air changes and no purge duration — not one figure. What it sets is a measurement: on a ventilation-only entry, 1910.146(c)(5)(ii)(E)(1) says an employee may not enter until the forced air ventilation has eliminated any hazardous atmosphere, and (c)(5)(ii)(C) says the atmosphere is tested with a calibrated direct-reading instrument before anyone goes in. A printed clock telling a crew the space is ready in eleven minutes would be read as permission. The instrument gives permission; the clock never does.

This generator produces a template. It does not establish compliance with 1910.146, 1926 Subpart AA or your employer's permit space program, it does not set acceptable entry conditions for any space, and it is not a substitute for the training 1910.146(g) and 1926.1207 require. Have a qualified person adapt it to your spaces before using it.

Frequently asked questions

Oxygen first, then combustible gases and vapors, then toxic gases and vapors. That order is written into 29 CFR 1910.146(d)(5)(iii) and repeated for construction at 1926.1204(e)(3), and Appendix B to 1910.146 explains why: most combustible gas meters are oxygen dependent and will not give a reliable reading in an oxygen-deficient atmosphere, and the threat of fire or explosion is both more immediate and, in most cases, more life threatening than toxic exposure. The columns of this log are in that order on purpose.

1910.146(b) defines a hazardous atmosphere by five causes: a flammable gas, vapor or mist above 10 percent of its lower flammable limit; airborne combustible dust at or above its LFL, which the standard says may be approximated as dust that obscures vision at 5 feet or less; an oxygen concentration below 19.5 percent or above 23.5 percent; any substance above the dose or permissible exposure limit published in subpart G or subpart Z; and any other atmospheric condition that is immediately dangerous to life or health. The acceptable entry conditions for a specific space are set by your entry supervisor and can be tighter than those numbers.

From Appendix D to 1910.146, the sample permits OSHA publishes in the standard itself, which are in the public domain. Appendix D-2 lists oxygen 19.5 percent to 23.5 percent, lower flammable limit under 10 percent, carbon monoxide 35 ppm as an 8-hour time-weighted average and hydrogen sulfide 10 ppm as an 8-hour TWA with a 15 ppm short-term limit. They are offered as a starting point and every field is editable, because the acceptable entry conditions belong to the space and to the person who signs the permit.

1910.146(d)(5)(ii) says test or monitor as necessary to determine whether acceptable entry conditions are being maintained — a performance requirement, not a fixed interval. In construction, 1926.1204(e)(2) goes further: monitor continuously unless you can demonstrate that continuous monitoring equipment is not commercially available for that hazard, or that periodic monitoring is frequent enough to keep the hazard controlled. OSHA's own sample permit in Appendix D-2 asks for continuous monitoring results to be recorded every two hours, which is a reasonable default for a written log when continuous instruments are in use.

At least the minimum response time the instrument manufacturer specifies — Appendix B(3) to 1910.146 puts it exactly that way. Sampling a space through a probe or a long hose takes longer than most people wait, and a short draw reads clean air from the tube rather than the atmosphere in the space. This log has a field for the manufacturer's response time so the number is on the paper, not in somebody's memory.

Appendix B(4) covers it. When you are monitoring an entry that involves a descent into an atmosphere that may be stratified, test the atmospheric envelope about 4 feet in the direction of travel and to each side, and if a sampling probe is used, slow the rate of progress to accommodate the sampling speed and the detector response. Heavier-than-air gases pool at the bottom, methane collects at the top, and a reading taken at the manhole rim describes the manhole rim.

Everyone leaves. On a ventilation-only entry, 1910.146(c)(5)(ii)(G) sets three steps in order: each employee leaves the space immediately, the space is evaluated to determine how the hazardous atmosphere developed, and measures are implemented to protect employees before any subsequent entry. On a full permit entry, an out-of-range reading is a prohibited condition, the attendant orders evacuation under 1910.146(i)(6)(i), and the entry supervisor terminates the entry and cancels the permit under 1910.146(e)(5)(ii). This log has a section for recording that sequence, because the reading that caused it is the one an investigator will ask about.

Yes, and it is not optional. 1910.146(d)(5)(iv) gives each authorized entrant or their authorized representative the opportunity to observe the pre-entry and any subsequent testing; (d)(5)(v) requires the employer to reevaluate the space in the presence of an entrant who asks for it because they have reason to believe the evaluation may not have been adequate; and (d)(5)(vi) requires the results of any testing to be provided to them immediately. The construction standard repeats all three at 1926.1204(e)(4)-(6). The sign-off block on this log records that it happened.

No, deliberately. 1910.146 sets no flow rate, no number of air changes and no purge duration anywhere, and a printed clock would be read as permission to enter. You ventilate, you measure with a calibrated direct-reading instrument, and the measurement is what authorizes entry — not the elapsed time.

Sources & references

Content checked against these sources — last reviewed August 28, 2026.

By — Editorial team of SteelToeTools.com (published by LSEA SAS) Updated v1