i have a couple of meters that i got from scrapping out some decommissioned labs years ago. they work. one is  smaller handheld the other is a larger unit with a remote probe.

fun to play with but to be honest virtually worthless as a prep item in the real world. if you find yourself in a location where you need one.. you are already screwed for the most part. this would be much more useful if you were outside the area and using it to check in coming people and supplies for contamination. even then without training and equipment it won't matter much.

there is a good bit to know about moving around in a contaminated area even in an evac. in general if you are close enough to an event to be worried about rad levels your likely already in the dangerous levels area. coms will be down and the likely hood of knowing where or even which way to go at that time will be very limited. levels don't really come into play that much and money would be much better spent on enough PPE to get you through several days/weeks of foot travel. without PPE there will be NO "good time" to leave the area as your getting constant exposure and low levels over time are as bad as high levels as exposure tends to be cumulative in most cases.

http://www.epa.gov/radiation/understand/health_effects.html


What kinds of health effects does exposure to radiation cause?
In general, the amount and duration of radiation exposure affects the severity or type of health effect. There are two broad categories of health effects: stochastic and non-stochastic.

Stochastic Health Effects

Stochastic effects are associated with long-term, low-level (chronic) exposure to radiation. ("Stochastic" refers to the likelihood that something will happen.) Increased levels of exposure make these health effects more likely to occur, but do not influence the type or severity of the effect.

Cancer is considered by most people the primary health effect from radiation exposure. Simply put, cancer is the uncontrolled growth of cells. Ordinarily, natural processes control the rate at which cells grow and replace themselves. They also control the body's processes for repairing or replacing damaged tissue. Damage occurring at the cellular or molecular level, can disrupt the control processes, permitting the uncontrolled growth of cells cancer This is why ionizing radiation's ability to break chemical bonds in atoms and molecules makes it such a potent carcinogen.

Other stochastic effects also occur. Radiation can cause changes in DNA, the "blueprints" that ensure cell repair and replacement produces a perfect copy of the original cell. Changes in DNA are called mutations.

Sometimes the body fails to repair these mutations or even creates mutations during repair. The mutations can be teratogenic or genetic. Teratogenic mutations are caused by exposure of the fetus in the uterus and affect only the individual who was exposed. Genetic mutations are passed on to offspring.

Non-Stochastic Health Effects

Non-stochastic effects appear in cases of exposure to high levels of radiation, and become more severe as the exposure increases. Short-term, high-level exposure is referred to as 'acute' exposure.

Many non-cancerous health effects of radiation are non-stochastic. Unlike cancer, health effects from 'acute' exposure to radiation usually appear quickly. Acute health effects include burns and radiation sickness. Radiation sickness is also called 'radiation poisoning.' It can cause premature aging or even death. If the dose is fatal, death usually occurs within two months. The symptoms of radiation sickness include: nausea, weakness, hair loss, skin burns or diminished organ function.

Medical patients receiving radiation treatments often experience acute effects, because they are receiving relatively high "bursts" of radiation during treatment.


Is any amount of radiation safe?
There is no firm basis for setting a "safe" level of exposure above background for stochastic effects. Many sources emit radiation that is well below natural background levels. This makes it extremely difficult to isolate its stochastic effects. In setting limits, EPA makes the conservative (cautious) assumption that any increase in radiation exposure is accompanied by an increased risk of stochastic effects.

Some scientists assert that low levels of radiation are beneficial to health (this idea is known as hormesis).

However, there do appear to be threshold exposures for the various non-stochastic effects. (Please note that the acute affects in the following table are cumulative. For example, a dose that produces damage to bone marrow will have produced changes in blood chemistry and be accompanied by nausea.)


Exposure(rem)  Health Effect(without treatment)Time to Onset

5-10                        changes in blood chemistry
50                                    nausea                                        hours
55                                    fatigue
70                                   vomiting
75                                     hair loss                            2-3 weeks
90                                    diarrhea
100                                  hemorrhage
400                                possible deathwithin                     2 months
1,000               destruction of intestinal lining
                             internal bleeding
                                      and death                           1-2 weeks
2,000            damage to central nervous system
                          loss of consciousness;                     minutes
                                      and death                          hours to days


how long will it take your family on foot to travel 25-50+ miles miles wearing PPE and carrying supplies? 2-3 days? longer? even if your on the low end of the exposure curve in that time you have enough to be pushing lethal longer term levels. mix in the 100's or thousands of others moving out with you and an expectation of advanced care is pretty much nil. surviving an initial blast is easy. surving a few weeks after the event is the hard part.

nukes are really one of those event where if it affects you, your fucked. many techs at fukushima died even getting to PPE with a small reactor event. anything large scale is pretty much game over for any expectation of long term survival. frankly i'd prefer to eat a bullet than die that way.

jmho

yup.. i was on the bio side of the house and anyone that thinks they are going to live and work in this stuff for a few days is living in a fantasy land. a few hours is literally debilitating to someone not used to wearing it everyday.