Ionizing radiation definitions

Radiation includes ionizing emissions such as alpha, beta, gamma, X‑rays, neutrons, high‑speed electrons, high‑speed protons, and other atomic particles. This definition comes from 1910.1096(a)(1) and excludes non‑ionizing waves like sound, radio waves, visible light, infrared, and ultraviolet light.

Radioactive material is any material that emits corpuscular or electromagnetic radiation by spontaneous nuclear disintegration. That is the definition in 1910.1096(a)(2), and it means materials that self‑emit ionizing particles or photons due to nuclear decay.

A restricted area is any area where the employer controls access to protect people from exposure to radiation or radioactive materials; an unrestricted area is any area not access‑controlled for that protection purpose. These definitions are in 1910.1096(a)(3) and 1910.1096(a)(4). Use the restricted/unrestricted distinction to decide where controls, monitoring, or posting are needed.

Dose means the quantity of ionizing radiation absorbed per unit mass by the body or part of the body. That definition appears in 1910.1096(a)(5). Employers and health‑physics professionals use dose units (see rad and rem) to evaluate and limit worker exposures.

A rad is a unit of absorbed dose equal to 100 ergs per gram of tissue; a rem is a unit that weights absorbed dose by its estimated biological effect compared to X‑rays. These unit definitions are in 1910.1096(a)(6) and 1910.1096(a)(7). Put simply: rad quantifies energy absorbed, rem adjusts that energy for expected biological harm.

The equivalents to 1 rem are: 1 roentgen of X‑ or gamma rays; 1 rad of X‑, gamma‑, or beta radiation; 0.1 rad of neutrons or high‑energy protons; 0.05 rad of particles heavier than protons that can reach the eye lens; or, for neutrons, 14 million neutrons/cm² incident on the body if flux is easier to measure. These equivalences are listed in 1910.1096(a)(7) and its subparagraphs.

Employers may assume 14 million neutrons per cm² incident on the body equals 1 rem when neutron flux is easier to measure, or they can estimate equivalent values from Table G‑17 if energy distribution is known. This allowance and the table are in 1910.1096(a)(7)(v). Use the table to convert neutron energy flux into dose equivalents for compliance and monitoring.

For X‑ or gamma rays up to 3 MeV, dose limits in the section may be assumed equivalent to the "air dose," meaning measurements in air can be used for compliance. That guidance is in 1910.1096(a)(8). Employers can therefore use appropriate air‑kerma or similar instruments for assessing compliance for energies up to 3 MeV.

Except as allowed by paragraph (b)(2), employers must not cause any individual in a restricted area to receive more than the quarterly doses in Table G‑18: 1.25 rem to whole body/head/trunk/active blood‑forming organs/lens/gonads; 18.75 rem to hands/forearms/feet/ankles; and 7.5 rem to skin of whole body. These limits are in 1910.1096(b)(1). Use these values when planning exposure controls and monitoring.

An employer may allow higher whole‑body doses provided: (1) no more than 3 rem in any calendar quarter; (2) the added dose plus the individual's accumulated occupational dose does not exceed 5(N−18) rems (N = age in years); and (3) the employer keeps adequate past and current exposure records showing the limits are not exceeded. These conditions are in 1910.1096(b)(2). Maintain clear records before authorizing higher exposures.

Employees under 18 may not receive in any calendar quarter more than 10 percent of the limits in Table G‑18. That restriction is stated in 1910.1096(b)(3). In practice, treat minors as having much lower allowable exposures and plan operations and monitoring accordingly.

A calendar quarter is any 3‑month period determined either by choosing a start date in January with corresponding April/July/October starts, by four 13‑week periods, or by the alternate 14/12/14/12 week split; rules for partial weeks at year start/end are provided. See the specific timing rules in 1910.1096(b)(4). Use whichever quarter method you adopt consistently and document it.

Employers must ensure airborne radioactive material concentrations in restricted areas do not exceed the limits in Table I of Appendix B to 10 CFR Part 20, averaged for a 40‑hour workweek; if hours differ, limits are increased or decreased proportionally. For individuals under 18, use Table II with averaging periods not greater than one week. These requirements are in 1910.1096(c)(1) and 1910.1096(c)(2), and refer to 10 CFR part 20 for the table limits.

No—"exposed" means present in the airborne concentration and no allowance is made for protective clothing, equipment, or particle size when determining compliance with airborne concentration limits. This is explicitly stated in 1910.1096(c)(3). Employers must control airborne levels by engineering and administrative means, not by relying on protective clothing to lower reported concentration values.

A survey is an evaluation of radiation hazards from the production, use, release, disposal, or presence of radioactive materials or other sources under specific conditions and includes physical location checks and measurements when appropriate. Employers must make necessary surveys to comply with the section, as required by 1910.1096(d)(1). Conduct surveys whenever conditions, operations, or materials could affect worker exposures.

Employers must supply and require use of personnel monitoring equipment (film badges, pocket dosimeters, etc.) for each employee who enters a restricted area under circumstances likely to produce a dose exceeding 25% of the applicable quarterly limit, for employees under 18 when likely to exceed 5% of the limit, and for anyone entering a high radiation area. These provisions are in 1910.1096(d)(2) and its subparagraphs.

A radiation area is any accessible area where a major portion of the body could receive more than 5 millirem in 1 hour or more than 100 millirem in any 5 consecutive days; a high radiation area is where a major portion of the body could receive more than 100 millirem in 1 hour. These definitions are in 1910.1096(d)(3)(ii) and 1910.1096(d)(3)(iii). Use these thresholds to classify areas and set posting and access controls.

Personnel monitoring equipment means devices designed to be worn or carried to measure the dose received (for example, film badges, pocket chambers, pocket dosimeters, film rings). Its purpose is to record individual doses for compliance and worker protection as defined in 1910.1096(d)(3)(i). Employers must select appropriate devices based on the type and energy of radiation.

Radiation caution signs must use the conventional three‑bladed radiation symbol in magenta or purple on a yellow background. That requirement is in 1910.1096(e)(1)(i). Use that symbol and color scheme on posted signs to clearly indicate radiation hazards.

Each high radiation area must be conspicuously posted with the radiation symbol and the words "CAUTION HIGH RADIATION AREA" and must have a control device that either reduces radiation levels on entry below the 100 millirem/hour threshold or energizes a conspicuous visible or audible alarm to notify the entrant and employer/supervisor, except for high radiation areas established for 30 days or less. These rules are in 1910.1096(e)(3)(i) and 1910.1096(e)(3)(ii). Ensure alarms or engineered controls are tested and maintained.

Under 1910.1096(e)(4)(i), an "airborne radioactivity area" is any room, enclosure, or operating area where airborne radioactive materials exceed specified concentrations in 10 CFR Part 20. Specifically, an area is an airborne radioactivity area if concentrations exceed the amounts in column 1 of Table 1 of appendix B to 10 CFR part 20, or if the weekly time-weighted average exceeds 25 percent of those amounts. See the definition in 1910.1096(e)(4)(i) and the referenced limits in 10 CFR part 20.

You must conspicuously post each airborne radioactivity area with the radiation caution symbol and the words "CAUTION AIRBORNE RADIOACTIVITY AREA." This posting requirement is specified in 1910.1096(e)(4)(ii). Ensure signs are visible at entrances and locations where workers could reasonably enter the area.

Rooms or areas where radioactive material (other than natural uranium or thorium) exceeds 10 times the quantity in appendix C to 10 CFR part 20 must be posted "CAUTION RADIOACTIVE MATERIALS." For natural uranium or thorium, posting is required when the amount exceeds 100 times the appendix C quantity. See 1910.1096(e)(5)(i) and 1910.1096(e)(5)(ii). The appendix C thresholds are in 10 CFR part 20, which you should consult to determine the numeric quantities (10 CFR part 20).

Each container that transports, stores, or is used to hold radioactive material above the appendix C quantity must bear a durable, clearly visible label with the radiation caution symbol and the words "CAUTION RADIOACTIVE MATERIALS." For natural uranium or thorium in quantities greater than 10 times the appendix C values the same labeling is required. See 1910.1096(e)(6)(i) and 1910.1096(e)(6)(ii).

A label is not required if the concentration in the container does not exceed the value in column 2 of Table 1 of appendix B to 10 CFR part 20, or for transient laboratory containers (like beakers, flasks, and test tubes) used while the user is present. See the exceptions in 1910.1096(e)(6)(iii) and the concentration limits in 10 CFR part 20.

Labels on containers used for storage must also state the quantities and kinds of radioactive materials in the container and the date the quantities were measured. This requirement is in 1910.1096(e)(6)(iv). Ensure stored-container labels remain durable and legible over time.

A room or area containing a sealed source does not need posting if the radiation level 12 inches from the surface of the source container or housing does not exceed 5 millirem per hour. This exemption is stated in 1910.1096(g)(1). If readings are above that value, the appropriate caution posting is required.

Rooms or other areas in onsite medical facilities are not required to be posted for the presence of patients containing radioactive material provided that personnel are in attendance who will take the precautions necessary to prevent exposures in excess of the limits in the standard. See 1910.1096(g)(2). Employers must still ensure those attendants enforce required safety measures.

Caution signs are not required for areas containing radioactive materials for periods of less than 8 hours if (1) the materials are constantly attended during those periods by an individual who will take precautions to prevent exposures over the limits and (2) the area is under the employer's control. See the conditions in 1910.1096(g)(3) and its subparts 1910.1096(g)(3)(i) and 1910.1096(g)(3)(ii).

Yes. Radioactive materials packaged and labeled in accordance with Department of Transportation regulations in 49 CFR Chapter I are exempt from the subpart's labeling and posting requirements during shipment, provided inside containers are labeled per paragraph (e). See the exemption in 1910.1096(h) and the DOT rules at 49 CFR Chapter I.

The evacuation warning signal must produce a midfrequency complex sound wave between 450 and 500 Hz modulated at 4–5 Hz, and the system must produce at least 75 decibels at every location where immediate evacuation is essential; enough signal units must be installed to meet this level everywhere, and the signal must be unique in the facility. These requirements are in 1910.1096(f)(1)(i) and 1910.1096(f)(1)(ii)–1910.1096(f)(1)(iv).

Yes. The signal-generating system must respond automatically to an initiating event without human action to sound the signal, and it must produce the required signal each time it is activated within one-half second of activation. These requirements are in 1910.1096(f)(1)(vi) and 1910.1096(f)(2)(i). Design the system so activation and delivery meet these timing objectives.

The signal-generating system must have an automatically activated secondary power supply adequate to simultaneously power all connected emergency equipment during a power failure, except when batteries are the primary power source. This is required by 1910.1096(f)(2)(ii). Ensure the secondary power engages automatically when main power is lost.

You must perform initial tests and inspections to verify fabrication and installation, and then conduct periodic tests and checks to minimize malfunctions. After major alterations, repeat initial-type tests. Tests must minimize hazards and include verification of power sources, calibration stability, trip levels, continuity of function with loss/return of services, indicators, and trouble circuits. Periodic scheduled performance tests (including sounding the signal and checking sound levels) must be done, with the entire system operationally tested at least quarterly; employees who may be present must be made familiar with the signal. See 1910.1096(f)(3) and its detailed subparts including 1910.1096(f)(3)(v) and 1910.1096(f)(3)(vii).

Testing must determine that the sound level of the signal meets the minimum 75 dB requirement at all locations requiring immediate evacuation, as specified in 1910.1096(f)(3)(v)(h) and 1910.1096(f)(1)(ii). Measure at representative work locations and document results.

If materials are present less than 8 hours and you omit posting, the materials must be constantly attended by someone who will take precautions to prevent exposures above the limits, and the area must be under employer control. These two conditions are required by 1910.1096(g)(3)(i) and 1910.1096(g)(3)(ii). Keep records of the attendance and control measures when relying on this exemption.

Employers must inform all individuals working in or frequenting any portion of a radiation area about the presence of radioactive materials or radiation, instruct them on safety problems and precautions to minimize exposure, inform them of applicable provisions of the section, and advise them how to request reports of their radiation exposure. Employers must also post a current copy of the standard and operating procedures or keep them available for employee inspection. See 1910.1096(i)(2) and 1910.1096(i)(3). Ensure training materials and posting locations are accessible to employees.

Radioactive materials stored in a non-radiation area must be secured against unauthorized removal from the storage place. This storage-security requirement is stated in 1910.1096(j). Use physical controls (locks, access restrictions) and inventory procedures to prevent unauthorized access or removal.

You must immediately notify OSHA by telephone or telegraph if an incident involves exposures at or above the thresholds listed in 1910.1096(l)(1)(i).

• Whole-body exposure of 25 rems or more.
• Skin (whole body) exposure of 150 rems or more.
• Exposure of the feet, ankles, hands, or forearms of 375 rems or more.

Cite: Notification of incidents, 1910.1096(l)(1)(i).

You must immediately notify OSHA if the released radioactive material, averaged over 24 hours, would exceed 5,000 times the limit in Table II of appendix B to 10 CFR part 20, per 1910.1096(l)(1)(ii).

• Use the limits specified in Table II of appendix B to 10 CFR part 20 for the comparison. See 10 CFR part 20 for the referenced limits.

Cite: 1910.1096(l)(1)(ii) and 10 CFR part 20.

You must notify OSHA by telephone or telegraph within 24 hours if an incident involves exposures at or above the lower thresholds listed in 1910.1096(l)(2)(i).

• Whole-body exposure of 5 rems or more.
• Skin (whole body) exposure of 30 rems or more.
• Exposure of the feet, ankles, hands, or forearms of 75 rems or more.

Cite: Twenty-four hour notification, 1910.1096(l)(2)(i).

You must submit a written report to OSHA within 30 days describing each exposure that exceeds any applicable limit, as required by 1910.1096(m)(1).

The written report must describe:

• The extent of exposure of persons to radiation or radioactive material.
• The levels of radiation and concentrations of radioactive material involved.
• The cause of the exposure and levels/concentrations.
• Corrective steps taken or planned to prevent recurrence.

Cite: Reports of overexposure and excessive levels and concentrations, 1910.1096(m)(1).

Yes. You must notify any employee who was exposed of the nature and extent of the exposure in writing when you report the overexposure to OSHA, per 1910.1096(m)(2).

• The notice must be in writing and explain the nature and extent of the exposure.
• The notice must include the statement: "You should preserve this report for future reference." as required by the section.

Cite: 1910.1096(m)(2).

You must maintain records of radiation exposure for all employees who require personnel monitoring under 1910.1096(d) and keep them in the same units used in the tables in paragraph (b) and in appendix B to 10 CFR part 20, per 1910.1096(n)(1) and (n)(2).

• Maintain individual exposure records for monitored employees and advise them of their exposure at least annually.
• Use the dose units shown in paragraph (b) of 1910.1096 and the units in appendix B to 10 CFR part 20.

Cite: Records, 1910.1096(n)(1)–(2).

You must furnish a former employee, within 30 days of the request, a written report of the employee's radiation exposure covering each calendar quarter (or a lesser period requested), per 1910.1096(o)(1).

• The report must include results of any calculations and analyses of radioactive material deposited in the body.
• The report must be in writing and include the statement: "You should preserve this report for future reference.".

Cite: Disclosure to former employee, 1910.1096(o)(1).

Employers who possess or use Atomic Energy Act materials under a Nuclear Regulatory Commission (NRC) license or in accordance with 10 CFR part 20 are deemed to be in compliance with 1910.1096 for those materials, per 1910.1096(p)(1).

• NRC licensees complying with 10 CFR part 20 are covered by 1910.1096(p)(1).
• NRC contractors operating NRC facilities are covered under 1910.1096(p)(2).
• Employers licensed by NRC-agreement States operating under those State requirements are deemed in compliance under 1910.1096(p)(3).

Cite: 1910.1096(p)(1)–(3).

You may not dispose of radioactive material except by transfer to an authorized recipient or in a manner approved by the NRC or a State named in 1910.1096(p)(3), as required by the disposal prohibition in 1910.1096.

• Disposal must be to an authorized recipient or follow NRC/Agreement State-approved procedures.
• Check whether your State is listed among the NRC-agreement States in 1910.1096(p)(3) before relying on State approvals.

Cite: [No employer shall dispose of radioactive material except..., 1910.1096] (https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.1096).

You must notify the Assistant Secretary of Labor or his duly authorized representative by telephone or telegraph of incidents that meet the criteria in 1910.1096(l), except that employees protected by NRC or certain Agreement State requirements follow those agencies' notification rules per 1910.1096(p).

• For employees not protected by NRC/Agreement State coverage, notify OSHA under the thresholds in 1910.1096(l)(1) and 1910.1096(l)(2).
• If the work is under an NRC license or an Agreement State program found compatible under 1910.1096(p)(3), follow the NRC/State reporting requirements instead.

Cite: Notification of incidents, 1910.1096(l) and NRC/NRC-Agreement State exceptions, 1910.1096(p).