F.A.Q. about Radiation Detectors

Q: Who Needs Radiation Detection Instruments? A: The reasons for acquiring a radiation detecting survey meter, Geiger counter and/or dosimeter are as varied as are peoples concerns for the future and the safety of their families in this ever changing world. Radiation threats are unique in that you can't see, smell, taste, hear or feel them, until it's already done its damage and you are suffering the effects. Without a radiation detector you would have to depend solely on the limited resources of the authorities to monitor your location, then determine your risk level, decide the best protective action and then to 'get the word out'.

Exclusively depending on others to monitor, evaluate, warn and advise you, in a rapidly developing nuclear emergency crisis, would surely not be anywhere near as quick in revealing your current risk as when you are capable of taking your own independent radiation readings. Also, where authorities are warning of radiation fallout not yet arrived, but anticipated to be heading your way, with a radiation meter you'll be able to confirm that the suggested protective action is in fact reducing your exposure and not inadvertently increasing it. (Safe avenues of evacuation and/or designated safe areas can potentially shift as quickly as the wind!)



Nuclear materials processing plant accidents (Tokaimura, Japan)

Nuclear waste (radioactive waste from hospitals, spent fuel and radioactive waste from nuclear power plants, radioactive contaminated materials, etc.) storage or processing facilities mishaps

Nuclear waste transport truck or train accidents



Lost or stolen radioactive sources (Over the last 50 years, incidents of lost and stolen licensed radioactive devices occur at the rate of once every other day. See Lost and Stolen Nuclear Materials in the United States)

Nuclear terrorism here via...

An attack on, or sabotage of, a nuclear power plant.

Or, a real terrorist atomic bomb detonated here

Or, much more likely, conventional explosives used to disperse radioactive materials to effectively contaminate an area and much within in it (i.e. DIRTY NUKE)

Limited nuclear war overseas with the fallout carried here by the wind (See Trans-Pacific Fallout for threat here if any of the 'players' went nuclear in the Mid-East, or Pakistan, India, Korea, China, Russia, etc.)

Nuclear War involving a direct attack upon the USA.

Regarding radioactive fallout and minimizing the effects on your family with the use of a radiation meter, Cresson H. Kearny, the author of Nuclear War Survival Skills, Original Edition Published September, 1979, by Oak Ridge National Laboratory, a Facility of the U.S. Department of Energy (Updated and Expanded 1987 Edition) states in Chapter 10 - Fallout Radiation Meters: A survivor in a shelter that does not have a dependable meter to measure fallout radiation or that has one but lacks someone who knows how to use it will face a prolonged nightmare of uncertainties. Human beings cannot feel, smell, taste, hear, or see fallout radiation.

Which parts of the shelter give the best protection? How large is the radiation dose being received by each person? When is it safe to leave the shelter for a few minutes? When can one leave for an hour's walk to get desperately needed water? As the fallout continues to decay, how long can one safely work each day outside the shelter? When can the shelter be left for good? Only an accurate, dependable fallout meter will enable survivors to answer these life-or-death questions.

With a reliable dose rate meter you can quite quickly determine how great the radiation dangers are in different places, and then promptly act to reduce your exposure to these unseen, unfelt dangers. For example, if you go outside an excellent fallout shelter and learn by reading your dose rate meter that you are being exposed to 30 R/hr, you know that if you stay there for one hour you will receive a dose of 30 R. But if you go back inside your excellent shelter after 2 minutes, then while outside you will have received a dose of only 1 R.

Bottom Line: Having on-hand an inexpensive radiation detecting meter in this day and age is cheap family insurance and, like major medical insurance, we can also hope & pray never to have to use it! Also, like any real insurance, it'll be near impossible to get it after the fact!

Q: What's the Difference Between Alpha, Beta and Gamma Radiation? A: Everything in nature would prefer to be in a relaxed, or stable state. Unstable atoms undergo nuclear processes that cause them to become more stable. One such process involves emitting excess energy from the nucleus. This process is called radioactivity or radioactive decay. "Radiation" and "radioactivity" are often confused, the proper relationship is that "radioactive atoms emit radiation."

The three main types of nuclear radiation emitted from radioactive atoms are:

Alpha: These are actual particles that are electrically charged and are commonly referred to as alpha particles. Alpha particles are the least penetrating of the three primary forms of radiation, as they cannot travel more than four to seven inches in air and a single sheet of paper or the outermost layer of dead skin that covers the body will stop them. However, if alpha particle emitting radioactive material is inhaled or ingested, they can be a very damaging source of radiation with their short range being concentrated internally in a very localized area.

Beta: These are also actual particles that are electrically charged and are commonly referred to as beta particles. Beta particles travel faster and penetrate further than alpha particles. They can travel from a few millimeters up to about ten yards in open air depending on the particular isotope and they can penetrate several millimeters through tissue. Beta particle radiation is generally a slight external exposure hazard, although prolonged exposure to large amounts can cause skin burns and it is also a major hazard when interacting with the lens of the eye. However, like alpha particles, the greatest threat is if beta particle emitting radioactive material is inhaled or ingested as it can also do grave internal damage.

Gamma: Gamma rays are similar to x-rays, they are a form of electromagnetic radiation. Gamma rays are the most hazardous type of external radiation as they can travel up to a mile in open air and penetrate all types of materials. Since gamma rays penetrate more deeply through the body than alpha or beta particles, all tissues and organs can be damaged by sources from outside of the body. Only sufficiently dense shielding and/or distance from gamma ray emitting radioactive material can provide protection.

Bottom Line: All three of the primary types of radiation above can be a hazard if emitted from radioactive material that was inhaled or ingested. Protected food and water and even a simple inexpensive dust protector face mask can go a long ways to denying this route of entry. However, for the penetrating gamma rays, it is essential to be able to measure the strength of this type of radiation to then discover the best protected shielding and distance options available. Also, in a shelter or home, besides revealing the safest locations there, knowing the intensity of the local gamma radiation outside will better indicate when it is again safe. Or, safe enough to perform a brief essential chore outside. More information on the specific physical damage caused by gamma radiation is below in the section entitled: Which Survey Meter Would Be Best For My Needs?

Q: What's the Difference Between Roentgen, Rad and Rem Radiation Measurements? A: Since nuclear radiation affects people, we must be able to measure its presence. We also need to relate the amount of radiation received by the body to its physiological effects. Two terms used to relate the amount of radiation received by the body are exposure and dose. When you are exposed to radiation, your body absorbs a dose of radiation.

As in most measurement quantities, certain units are used to properly express the measurement. For radiation measurements they are...

Roentgen: The roentgen measures the energy produced by gamma radiation in a cubic centimeter of air. It is usually abbreviated with the capital letter "R". A milliroentgen, or "mR", is equal to one one-thousandth of a roentgen. An exposure of 50 roentgens would be written "50 R". Rad: Or, Radiation Absorbed Dose recognizes that different materials that receive the same exposure may not absorb the same amount of energy. A rad measures the amount of radiation energy transferred to some mass of material, typically humans. One roentgen of gamma radiation exposure results in about one rad of absorbed dose. Rem: Or, Roentgen Equivalent Man is a unit that relates the dose of any radiation to the biological effect of that dose. To relate the absorbed dose of specific types of radiation to their biological effect, a "quality factor" must be multiplied by the dose in rad, which then shows the dose in rems. For gamma rays and beta particles, 1 rad of exposure results in 1 rem of dose. Other measurement terms: Standard International (SI) units which may be used in place of the rem and the rad are the sievert (Sv) and the gray (Gy). These units are related as follows: 1Sv = 100 rem, 1Gy = 100 rad. Two other terms which refer to the rate of radioactive decay of a radioactive material are curie (Ci) and becquerel (Bq).

Bottom Line: Fortunately, cutting through the above confusion, for purposes of practical radiation protection in humans, most experts agree (including FEMA Emergency Management Institute) that Roentgen, Rad and Rem can all be considered equivalent. The exposure rates you'll usually see will be expressed simply in terms of roentgen (R) or milliroentgen (mR). For details on how much is too much "R", see the Q&A section below entitled: Which Survey Meter Would Be Best For My Needs?

Q: What's the Difference Between Survey Meters, Geiger Counters and Dosimeters? A: Survey meters, field survey meters, rate meters, radiac meters, radiation detection meters, low-range meters, high-range meters, airborne meters, fallout meters, remote monitors, Geiger counters, and even 'dose rate meters' are all describing instruments that measure exposure rate or the intensity of radiation at a location at some point in time. It's like the speedometer of a car; both present measurements relative to time. All of these above 'meters', the Geiger counter, too (which utilizes a Geiger tube rather than an ion chamber), will show their radiation intensity readings relative to time, such as R/hr or mR/hr like the scale at the right, same as a car speedometer will show miles/hr. If you entered a radioactive area and your meter says 60 R/hr then that means if you were to stay there for a whole hour you would be exposed to 60 R. Same as driving a car for an hour at 60 mph, you'd be 60 miles down the road after that hour, at that rate.

Dosimeters, which are also available in high or low ranges, can be in the form of a badge, pen/tube type, or even a digital readout and all measure exposure or the total accumulated amount of radiation to which you were exposed. (The Civil Defense pen/tube tube would show a reading like at the right when looking through it.) It's also similar to the odometer of a car; where both measure an accumulation of units. The dosimeter will indicate a certain total number of R or mR exposure received, just as the car odometer will register a certain number of miles traveled.



Q: How Good Are Surplus FEMA Civil Defense Survey Meters, Geiger Counters and Dosimeters? A: From the numerous FEMA technicians who have maintained, repaired and calibrated thousands of these Civil Defense Survey Meters, Geiger Counters and Dosimeters over many years, oftentimes even decades, we heard nothing but praise with a few specific maintenance cautions to be aware of. Most of these technicians have seen the same units come back in from active use in the field for their 1, 2 or 3 year re-calibration certification. (The calibration schedule varies based on the particular application they might be utilized for 'in the field'.) They know first-hand how well they hold up their calibration and can be counted on to perform. (Many thousands of these same exact type Civil Defense radiation survey meters and dosimeters are also deployed in various states and amongst their local governments First-Responders; the fire, police, EMT, and HazMat teams. Also found were a fair number of hospitals also utilize them to periodically check their X-Ray machines, etc. for leaks, too.)

All the technicians variously described the properly maintained, calibrated, and stored Civil Defense survey meter and dosimeter as "accurate", "reliable" and "dependable". Many of these same technicians and radiological officers are also atop the call lists in their respective states for any radiological emergency and many of these same survey meters and dosimeters are what they will be confidently responding with. They know them well and trust them.

However, surplus or auction acquired Civil Defense meters and dosimeters are often brought onto the market with little or none of their previous history known of their maintenance, repairs, last calibrations, and past storage conditions. Many of these units, unlike the reliability proven units described above and maintained on a regular basis, may have been out of that maintenance 'loop' for as long 10, 15 or 20 years. Or, they may be new-in-the-box units, produced in the 60's or 70's, that never even got into the maintenance 'loop'. The functionality, reliability and accuracy of any particular individual surplus Civil Defense meter or dosimeter can not be assumed, until actually verified and proven to be so. We know this from the experience of culling out the bad units from amongst the good as we've evaluated, tested, and had calibrations attempted on thousands of these same surplus meters. (We have over 100,000 of them here in an associated facility. See photos below.) Many of these surplus meters can be every bit as reliable and accurate as those described above, but it first requires a systematic evaluation and testing process to identify them. More on that essential process is covered below in the Q&A section entitled: "Where Can You Buy a Civil Defense Survey Meter?" and at "What's Two Tigers Radiological's Approach & Commitment?"

Bottom Line: We found the above sentiments by FEMA technicians so universal, and witnessed the successful tests and calibrations of enough regularly maintained meters, some often well past their scheduled re-calibrations, that we are confident that a properly maintained, calibrated, and stored Civil Defense Survey Meter or dosimeter will give its owner very reliable and accurate service. The goal then needs to be to acquire only a quality Civil Defense meter or dosimeter that is first proven to be fully up to these maintenance, calibration and storage standards.

The following is from Biological Effects of Radiation and is part of the Radiation Worker Training (RWT) common to all DOE facilities. It is instructive in outlining the levels of radiation and their effects.

4.2 ACUTE AND CHRONIC RADIATION DOSE Potential biological effects depend on how much and how fast a radiation dose is received. Radiation doses can be grouped into two categories, acute and chronic dose.

4.2.1 Acute dose

An acute radiation dose is defined as a large dose (10 rad or greater, to the whole body) delivered during a short period of time (on the order of a few days at the most). If large enough, it may result in effects which are observable within a period of hours to weeks.

Acute doses can cause a pattern of clearly identifiable symptoms (syndromes). These conditions are referred to in general as Acute Radiation Syndrome. Radiation sickness symptoms are apparent following acute doses >100 rad. Acute whole body doses of >450 rad may result in a statistical expectation that 50% of the population exposed will die within 60 days without medical attention.

As in most illnesses, the specific symptoms, the therapy that a doctor might prescribe, and the prospects for recovery vary from one person to another and are generally dependent on the age and general health of the individual.

Blood-forming organ (Bone marrow) syndrome (>100 rad) is characterized by damage to cells that divide at the most rapid pace (such as bone marrow, the spleen and lymphatic tissue). Symptoms include internal bleeding, fatigue, bacterial infections, and fever.

Gastrointestinal tract syndrome (>1000 rad) is characterized by damage to cells that divide less rapidly (such as the linings of the stomach and intestines). Symptoms include nausea, vomiting, diarrhea, dehydration, electrolytic imbalance, loss of digestion ability, bleeding ulcers, and the symptoms of blood-forming organ syndrome.

Central nervous system syndrome (>5000 rad) is characterized by damage to cells that do not reproduce such as nerve cells. Symptoms include loss of coordination, confusion, coma, convulsions, shock, and the symptoms of the blood forming organ and gastrointestinal tract syndromes. Scientists now have evidence that death under these conditions is not caused by actual radiation damage to the nervous system, but rather from complications caused by internal bleeding, and fluid and pressure build-up on the brain

Other effects from an acute dose include:

200 to 300 rad to the skin can result in the reddening of the skin (erythema), similar to a mild sunburn and may result in hair loss due to damage to hair follicles.

125 to 200 rad to the ovaries can result in prolonged or permanent suppression of menstruation in about fifty percent (50%) of women.

600 rad to the ovaries or testicles can result in permanent sterilization.

50 rad to the thyroid gland can result in benign (non cancerous) tumors.

As a group, the effects caused by acute doses are called deterministic. Broadly speaking, this means that severity of the effect is determined by the amount of dose received. Deterministic effects usually have some threshold level - below which, the effect will probably not occur, but above which the effect is expected. When the dose is above the threshold, the severity of the effect increases as the dose increases

Another perspective on the effects of radiation is from Bruce Beach and is excerpted from his page Radiation and Detectors:

The following is interpreted from attached "official" and other "expert" sources. These sources often provide a 'range' for effects, but I have simplified this to a single number to make the table easier to memorize - and you should memorize it. You can then 'extrapolate' for your self the relative severity of effects of a number between a higher and lower number.

600R -- means 100% chance of fatality is expected. Some much earlier - but last within two weeks.

400R -- means 50% will die within one to three weeks. Those that don't die are going to be VERY sick and wish that they would. After a few days some may feel better but will often then turn, sicken and die in a few weeks.

200R -- lots of sickness, and radiation sickness is pretty terrible (Think of cancer treatment without pain killers.) Lots of vomiting - hair falling out - and all that. Not nice

50R -- No fatalities at this level. There is a difference of opinion, as to whether the sickness at this level is physical. Some think that at this level the sickness is psychosomatic. Whatever its cause it is very general.

30R -- Most everyone will feel some sickness - - maybe just "punky" and it may be "just" psychosomatic but it certainly would not be beneficial for children and pregnant mothers. Even this level is a thousand times higher than the maximum general population exposure permitted under peacetime standards.

In the final analysis, fatality is probabilistic, somewhat like car accident fatalities. There have been cases of people getting very much higher radiation and surviving, and others with much lower who have not. Cause and effect become clouded when working with probability issues. There are many impinging factors, such as age, health, medical care, or lack of medical care.

F.A.Q. about Radiation Detectors
F.A.Q. about Radiation Detectors