Trending Topics

Time, distance, shielding: Minimizing radiation exposure

Establish warm, hot and cold zones; use PPE and distance to shield; and measure radiation throughout


First responders can encounter radioactive materials in any number of emergency response scenarios.


Watch just about any television drama and you’re more than likely to come across a storyline involving a potential “dirty bomb” or some other threat involving radioactive materials. It makes for gripping entertainment, however, first responders can encounter radioactive materials in any number of emergency response scenarios. In this article, we’ll discuss how to use time, distance and shielding to your advantage to safely, effectively and efficiently mitigate situations where radioactive materials are present.

What are radioactive materials?

Radiation is the process by which energy is emitted as either particles or waves. Broadly, it can take the form of sound, heat or light. However, most people generally use the term to refer to radiation from electromagnetic waves, ranging from radio waves, though the visible light spectrum, and up through to gamma waves.

Radioactive materials exist everywhere in nature and we barely give it a second thought. That is until we experience sunburn, which after all is a radiation exposure. As with a sunburn, the real effects of a radiation exposure may not be felt for many years after the initial exposure.

Protecting yourself in the field

When responding to an emergency that may involve radioactive material, or when you first learn of the presence of radioactive materials, here are three steps to take as an emergency responder to protect yourself and others.

1. Measure radiation

Use portable monitoring equipment to determine the type of radiation and its strength. Don’t think of yesterday’s Geiger counters. Instead, look for basic and multi-purpose radiation survey meters. These modern radiation detection devices can also provide more sophisticated measurements for a wide variety of applications.

2. Establish the cold, warm and hot zone

Use those readings to establish operational control zones:

  • Hot zone. Where meter readings are above permissible limits and personnel must be using the appropriate level of personal protection.
  • Warm zone. Where meter readings are well below permissible levels. The decontamination area is in the warm zone and serves as the gateway for exposed victims and first responders to leave the hot zone.
  • Cold zone. Where there are no detectable readings for radioactive materials. The Cold Zone is where patient care areas and first responder rehabilitation are located.

Radiation monitoring equipment must continue to be used in all control zones to ensure the integrity of the control zone and to ensure that radioactivity readings remain appropriate for each zone.

3. Time, distance, shielding

All personnel working in the hot zone must use the following principles regarding exposure to a hazardous material (in this case a radioactive material) to limit their personal exposure.

  • Time. Limit the time that you are near the material to the shortest possible period.
  • Distance. Distance is one of the most effective means to reduce dose thanks to basic principles of geometry. When the working distance from a radiation source is increased by a factor of two, the dose received from that source will be reduced by a factor of four. This is referred to as the inverse square law.
  • Shielding. Use protective clothing, equipment or physical barriers to prevent contamination from entering the body.

Putting it all together

So, let’s look at a possible scenario involving damage to a nuclear gauge on a road construction site and an injured worker. Nuclear gauges use radioactive sources to measure the thickness, density or make-up of a wide variety of materials and surfaces and are a critical tool for ensuring that roads are constructed to last.

  1. Wear your PPE and SCBA, and use your radiation survey monitor to approach the patient (shielding).
  2. Spend the shortest amount of time necessary in your PPE and SCBA to affect the removal of the injured worker (time).
  3. Doff your PPE and SCBA in the decontamination area and put distance between you and your contaminated gear (distance).

Using the principles of time, distance and shielding, in conjunction with today’s generation of radiation monitoring equipment, first responders can do their job safely, effectively and efficiently when encountering emergency situations where radioactive materials are present.

Battalion Chief Robert Avsec (ret.) served with the Chesterfield (Virginia) Fire & EMS Department for 26 years. He was an instructor for fire, EMS and hazardous materials courses at the local, state and federal levels, which included more than 10 years with the National Fire Academy. Chief Avsec earned his bachelor’s degree from the University of Cincinnati and his master’s degree in executive fire service leadership from Grand Canyon University. He is a 2001 graduate of the National Fire Academy’s EFO Program. Beyond his writing for and, Avsec authors the blog Talking “Shop” 4 Fire & EMS and has published his first book, “Successful Transformational Change in a Fire and EMS Department: How a Focused Team Created a Revenue Recovery Program in Six Months – From Scratch.” Connect with Avsec on LinkedIn or via email.