Posting radiation areas is one visible element of a radiation safety program, but the sign on a door or boundary is only one part of a larger survey, license, procedure, access-control, and training record. NRC Part 20 points to posting text in 10 CFR 20.1902, definitions in 10 CFR 20.1003, sign-symbol context in 10 CFR 20.1901, access-control context in 10 CFR 20.1601 and 20.1602, and exceptions in 10 CFR 20.1903.
This guide summarizes source context and review prompts. It does not determine legal posting, no-posting status, sign placement, individual monitoring, access controls, exceptions, Agreement State applicability, license conditions, or entry authorization. Final decisions need calibrated surveys, current procedures, and RSO or qualified health physics review.
Area Classifications and Dose Rate Thresholds
10 CFR 20.1003 defines area classifications using dose-rate and accessibility context. Radiation Area and High Radiation Area definitions use 30 cm from the source or from a surface that radiation penetrates. Very High Radiation Area context uses absorbed dose at 1 meter from a source or penetrated surface.
- Radiation Area prompt: source definition tied to dose equivalent in excess of 5 mrem in 1 hour at 30 cm.
- High Radiation Area prompt: source definition tied to dose equivalent in excess of 100 mrem in 1 hour at 30 cm.
- Very High Radiation Area prompt: source definition tied to absorbed dose in excess of 500 rads in 1 hour at 1 meter.
The unit and distance change for the very-high row matters. A 30 cm value derived from inverse-square math can be a local point-source screen, but it is not a legal conversion for every source, beam, shield, scatter field, pulsed field, or accessible surface. Accessibility, license conditions, procedures, and survey records still control how the source context is applied.
Area thresholds at a glance: Radiation Area source prompt: >5 mrem/hr at 30 cm. High Radiation Area source prompt: >100 mrem/hr at 30 cm. Very High Radiation Area source prompt: >500 rad/hr at 1 m. Treat these as source-context review rows until calibrated surveys and RSO procedures verify the field condition.
Radiation Area Posting Guide
Determine radiation area posting requirements from dose rate at 30 cm. Identifies Radiation Area, High Radiation Area, and Very High Radiation Area classifications per 10 CFR 20.1003 and 20.1902.
Sign Wording Source Context Under 10 CFR 20.1902
10 CFR 20.1902 gives source wording for radiation-area, high-radiation-area, very-high-radiation-area, airborne-radioactivity, and radioactive-material postings. 10 CFR 20.1901 gives the radiation-symbol color context. Use the current rule text, current license conditions, sign product, and site procedure before treating any wording as field-ready.
- Radiation Area source wording: "CAUTION, RADIATION AREA."
- High Radiation Area source wording: "CAUTION, HIGH RADIATION AREA" or "DANGER, HIGH RADIATION AREA."
- Very High Radiation Area source wording: "GRAVE DANGER, VERY HIGH RADIATION AREA."
- Airborne Radioactivity Area source wording: "CAUTION, AIRBORNE RADIOACTIVITY AREA" or "DANGER, AIRBORNE RADIOACTIVITY AREA."
Radioactive-material room posting and container labeling involve separate quantity, label, and information requirements. Sign visibility, placement, durability, size, supplemental information, and replacement practices must be verified under current RSO procedures and site conditions.
A mismatch between current survey conditions, the source definition, access controls, and sign wording can become a safety and compliance issue. Do not use a calculator row by itself to select or remove signs; verify the current survey and procedure record.
Access-Control Review for High and Very High Radiation Areas
High-radiation-area and very-high-radiation-area source rows need more than sign wording review. 10 CFR 20.1601 points to high-radiation-area entrance or access-point controls and allows specific alternatives. 10 CFR 20.1602 points to additional measures for very-high-radiation-area access. The correct control depends on the source, layout, license, procedure, occupancy, entry workflow, monitoring program, and qualified review.
Industrial radiography, machine-produced radiation, vaults, shielded gauges, and temporary boundaries can fall under additional rules or license conditions. A calculator row cannot choose locks, alarms, surveillance, interlocks, barrier spacing, dosimetry, written authorization, or emergency actions.
Use a high or very-high prompt as an escalation point for RSO and procedure review. Signs alone should never be treated as proof that access-control, monitoring, or authorization requirements have been satisfied.
Exceptions from Posting Requirements
10 CFR 20.1903 lists posting exceptions with conditions. Common review areas include less-than-8-hour attended radioactive-material use, certain patient rooms, sealed-source container or housing conditions, and teletherapy room conditions. Each exception requires the listed facts to be true and documented under current license and procedure controls.
Portable gauges, radiography devices, shielded gauges, and storage locations need current survey and source records before an exception can be relied on. Transport, storage, container labeling, radioactive-material quantity posting, and Agreement State terms may add separate requirements.
Use the exception list as a checklist for RSO review, not as automatic permission to omit or remove signs.
If a shielded gauge installation appears below the 5 mR/hr prompt at 30 cm, document the calibrated survey and verify the sealed-source exception, license terms, source housing condition, and any required labels with the RSO before treating it as a no-posting basis.
Container and Device Labeling
10 CFR 20.1904 requires that every container of licensed material bear a durable, clearly visible label with the radiation symbol, the words "CAUTION, RADIOACTIVE MATERIAL" (or "DANGER, RADIOACTIVE MATERIAL"), and sufficient information (isotope, quantity, date of measurement, radiation levels, name of responsible individual) to minimize exposure to individuals handling or using the container.
For sealed sources in shipping containers (Type A or Type B per DOT regulations), the manufacturer's labeling typically satisfies this requirement. For sources in storage (source pigs, gauge housings, camera storage boxes), verify that the label is present, legible, and current. Labels degrade from UV exposure, chemical exposure, and physical abrasion. Replace faded or damaged labels.
Some facilities add supplementary information to the label: the license number, emergency contact number, and the dose rate at 30 cm and 1 meter. This information is helpful for emergency responders and for anyone who encounters the container unexpectedly. For gauges mounted on process equipment, a sturdy metal tag attached to the gauge with wire or chain is more durable than an adhesive label.
Exemptions from container labeling under 10 CFR 20.1905 apply to containers holding material in quantities below the quantities listed in 10 CFR Part 20 Appendix C, certain laboratory containers in immediate use, and containers that are being processed (opening, transferring) by an individual who is present. The exemptions do not eliminate the need for area posting if the area thresholds are exceeded.
Implementing a Posting Review Program
A posting program should connect the sign, the survey record, the current source condition, the license condition, the access-control procedure, and worker training. Useful review practices include:
Survey before a posting decision. Do not rely on calculation or assumption alone. Use a calibrated instrument and current survey method at the applicable source or surface reference distance.
Update when conditions change. Source exchanges, shielding changes, beamline changes, damaged housings, decommissioned sources, storage changes, or procedure changes should trigger survey and posting review.
Verify sign products and placement. Confirm the current sign-symbol color context, wording, visibility, durability, and supplemental information under the current rule, license, and RSO procedure.
Train and audit under the program. Worker instruction, periodic walkthroughs, and records should be run under the facility radiation protection program rather than from a calculator output.
A periodic posting walkthrough should compare signs, survey records, source inventory, access controls, labels, and decommissioned locations against current procedures. Keep the cadence and documentation method under the facility program.
Common Posting Review Gaps
NRC and Agreement State programs can identify posting and labeling issues when the survey record, sign, access control, label, source condition, or procedure record does not line up. Common review gaps include:
Container label gaps. Storage and device labels need current source information, legibility, and procedure review.
High-radiation-area mismatch. A current survey above the high-radiation-area prompt needs access-control and monitoring review, not only a different sign word.
Access-control gaps. Locks, alarms, surveillance, authorization, and monitoring must be evaluated against the current rule, license, layout, and procedure.
Stale postings. Signs left after source removal or condition changes can confuse workers and should be reviewed under the radiation protection program.
Temporary work area gaps. Industrial radiography and temporary source use often involve separate boundaries, controls, and surveillance under license conditions or 10 CFR 34 or Agreement State rules.
Enforcement severity and corrective action depend on the current facts, license, agency program, prior history, and review record. Treat any high-radiation-area mismatch as an immediate RSO escalation item, not as a calculator cleanup task.