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OSHA/NIOSH Interim Guidance (February 2006)

Chemical - Biological - Radiological - Nuclear (CBRN) Personal Protective Equipment Selection Matrix for Emergency Responders

Radiological Dispersal Devices

A Radiological Dispersal Device (RDD), or "Dirty Bomb", is a conventional explosive device which has been surrounded with or contaminated with some form of radioactive material.  When it explodes, the device spreads the radioactive material over a wide area. The purpose of these devices is to frighten people and make buildings and land unusable during the weeks necessary to perform decontamination. In the most likely scenario, low-level radioactive powder or pellets would be used, and the contamination would be dispersed over a few city blocks. The actual radiation hazard would be dependant on the source material used. It is not likely that enough radiation would be present to cause severe illness in the exposed population.

Emergency responders to an explosion or the resulting fires will generally not know they are being exposed to radiation unless they utilize a radiation detecting device. There is no practical personal protective equipment (PPE) to protect First Responders against externally penetrating gamma radiation. Monitoring devices are the only means to ensure that responders do not enter an area where exposures to external gamma radiation is excessive.

Personal protective equipment (PPE) to prevent skin contamination of particulates is very effective against particulate-borne radiation hazards (i.e., alpha and beta particles). Typical fire fighter "turn-out" gear, including a SCBA, is generally adequate for this purpose. The use of turn-out gear or any disposable protective clothing suitable for particulate exposure, should be followed by appropriate decontamination of personnel and equipment.

Protection of internal organs from inhalation of radioactive particulates can be provided by wearing an appropriate particulate respirator. The SCBAs will provide the highest level of protection. Responders should utilize at least a full-face air-purifying respirator with a P-100 or HEPA filter, as appropriate. Respiratory protection specifically approved by NIOSH for CBRN exposures is desirable. However, where specific CBRN-approved respirators are not available, the incident commander may allow alternative NIOSH-approved respirators, such as SCBAs, or full-face powered or non-powered air-purifying respirators with P-100 or HEPA filters, as appropriate. It should be noted that these recommendations for respiratory protection are designed ONLY for protection against inhalation of radioactive particulates, and do not consider protection that may be necessary for other contaminants, such as chemical or biological agents.

Particulate sampling can be performed to measure the radioactivity of dust in the air and to further characterize exposures. Based on the sampling data, the respirator protection factor needed to meet the relevant exposure limits can be determined (see table below), and the specific type of respirator needed can be identified. According to the data, it may be possible to downgrade or remove requirements for respiratory protection. However, until exposures have been characterized, responders and support personnel should continue to utilize full-face air-purifying P100 respirators, or higher respiratory protection (e.g., SCBAs, PAPRs).

Guidance Matrix for RDD Incidents

OSHA Occupational Exposure Limits for Ionizing Radiation 29 CFR 1910.1096

Rems per calendar quarter

Whole Body; Head and Trunk; Active Blood-Forming Organs; Lens of Eye or Gonads

1 1/4

Hands and Forearms; Feet and Ankles

18 3/4

Skin of Whole Body

7 1/2

Under age 18 workers

10 percent of above limits

Over age 18 workers

3 rem may be permitted under conditions specified in 29 CFR 1910.1096(b)(2)

Note: The Department of Homeland Security is currently chairing an interagency workgroup which is in the process of assessing the protective action guidance for response to an RDD event.

Specific Hazard Information
Related Online Resources

This product is not a standard or regulation, and it has no effect on employers' legal obligations. The guidance is advisory in nature, informational in content, and is intended only as technical assistance to employers in providing a safe and healthful workplace during emergency response operations. This document does not enhance or diminish any existing obligations under the OSH Act. The information in this document is interim guidance only. It is anticipated that NIOSH CBRN approval for all classes of respirators will be available in the near future. This guidance will change at the time NIOSH CBRN certification standards are available for all respirator classes. OSHA also may update this guidance as additional information becomes available in the future.

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