User manual

RADON IN WATER:
If you find that you do have a build up of radon gas in your
house, and you suspect one source may be your water, you
can test for radon in water by buying an inexpensive activated
charcoal filter for your tap. After mounting the filter, run
your water at a medium rate for half an hour or so, while
holding the back of the RM-60 against the charcoal filter. Be
careful not to get the RM-60 wet. Any radon and radon
decomposition products should collect in the filter, causing it
to become radioactive. Any increase in your monitor’s read-
ing would indicate the presence of radon, or other radioactive
material, in your water, in which case you should call your
state or local health agency.
CHARCOAL CANISTERS:
A charcoal canister or alpha track test is a valuable addition
to your radon testing program, and it is a good idea to have
at least one charcoal canister test. The charcoal canister or
alpha track tests are calibrated to measure for radon gas in
picocuries radon per liter of air, whereas the RM-60 is cali-
brated to measure the level of ionizing radiation.
Your RM-60 does many things for you that a charcoal canis-
ter test cannot do. For example, in combination with an air
filter, the RM-60 rapidly samples a large quantity of air for
the highly radioactive decomposition products (daughter
products) of radon. Even without the assistance of a fan
forced air filter system, a room with significant levels of
radon will immediately produce higher background readings
on the computer, from the RM-60, over-and-above a room
without radon.
Also the RM-60 can continuously check for the presence of
radon gas as well as many other radioactive contaminations,
year around, and immediately warn you of a potential prob-
lem.
Never-the-less, you should not overlook the benefits of a
charcoal canister or alpha track test.
An interesting experiment might be to measure the level of
radiation from a charcoal canister with your RM-60 before
sending the canister back to have it tested.
A charcoal canister will become radioactive when sitting in a
radon infested area. The level of the ionizing radiation from
the canister is an indication of the quantity of radon the canis-
ter was exposed to, just as the level of ionizing radiation from
an air filter is an indication of the quantity of radon present.
You can use a charcoal canister test to calibrate an RM-60\fan
forced air filter combination, empirically, to picocuries radon
per liter of air, if you so desire, as follows:
1. Set up your fan forced air filter\RM-60 system and run the
fan for about two hours, until you reach equilibrium. Equilib-
rium is evident when the radioactive build-up on the filter
levels out. This occurs when enough daughter products are
collected on the filter such that the collected daughter prod-
ucts are decomposing at the same rate as they are being
collected.
2. Keep the fan running and periodically measure the radia-
tion level with your computer. At the same time, run a
charcoal canister test. The increase in radiation from the filter
system, above normal background, should correlate with the
level of radon per liter reported by the charcoal canister test.
A doubling of your reading from the filter would indicate a
doubling of the quantity of radon present.
RADON INDUCED RADIOACTIVITY OF AN AIR FILTER:
A detailed evaluation of a reading expected from a buildup of
radioactivity on an air filter, from decomposition of radon gas,
follows. An typical house might contain 20,000 cu. ft. of air
which equals 500,000 liters. At two picocuries of radon per
liter, this would equal one microcurie of radon in the house.
To maintain this level, there must be a continuous inward
flow of radon into the house of one microcurie/hr., given an
air exchange rate of one exchange/hr., to the absolute least
radon inflow of 0.25 microcurie/hr. in only the most super
insulated houses. The daughter products of radon gas should
produce a reading of 0.85 microroentgen/hr./microcurie, at one
meter, due to gamma flux from radium B (Pb., At. Wt. 214,
halflife, 26.8 minutes), radium C (Bi., At. Wt. 214, halflife,
19.7 minutes), radium C’ (Po., At. Wt. 214, halflife 1.5 x
10
-4
seconds) radium D (Pb., At. Wt. 210, halflife 22 years)
and radium E (Bi., At. Wt. 210, halflife 5.0 days). Essentially
all the gamma flux from radium is due to these daughter
products of radon. The intensity of radiation flux decreases
by the inverse of the square of the distance between source
and measuring point, therefore a reading of 0.85
microroentgens/hr. at one meter should produce a reading of
3.4 microroentgens per hr. at 0.5 meters, 13.6 microroentgens
per hr. at 0.25 meters and 54.4 microroentgens per hr. at
0.125 meters. At 4 picocuries per liter concentration, a 100%
efficient filter would produce an increase in reading of 26.6
microroentgens/hr. at 0.25 meters and 106.8 microroent-
gens/hr. at 0.125 meters, while a 35% efficient filter would
produce an increase in reading of 9.3 and 37.25 microroent-
gens/hr. respectively. Even higher readings could be expect-
ed, as the radon daughter products reach equilibrium on the
filter (radium B, halflife 26.8 minutes), due to the continuous
source of fresh radon that must be entering the house to main-
tain the picocurie per liter level. If a smaller, portable fan/air
filter combination were used, it would be placed in the base-
ment, the area with highest radon concentration.
Although there are many variables involved in the detection
of radon, the above illustrates that the RM-60, in combination
with an air filter, can detect the presence of very small levels
of radon gas.
As indicated above, past experience indicates that a RM-60
placed in the middle of a basement with about 2 picocuries
radon per liter air might display a background reading perhaps
5 to 10 MicroRs higher than normal, with puffs or spurts to
higher levels. Such an increase would not necessarily be
expected from an even distribution of the radon. A reservoir
of beta emitting daughter products in the form of radioactive
dust may explain the increase.
To double-check your conclusions about the presence of
radon, run at least one charcoal canister or alpha track test.
The small cost of a canister test as well as the benefits of the
RM-60 are well worth the cost and effort.
12