37 results about "Radon Daughters" patented technology

The invention discloses a method for rapidly measuring radon concentration by zero-order approximation, comprising measurement and calculation. At first, a radon measurement instrument is enabled to work under a scale mode, radon concentration is reversely deduced by using the counting of a long-time 218Po peak in a standardized radon chamber to obtain a scale factor, which is therefore equivalent to an RAD7 radon measurement instrument working under a sniff mode; the radon measurement instrument is then switched to work under a zero-order approximation mode, measurement cycle and cycle times are set, and after the radon measurement instrument is started up, the air outside is subjected to the filtration of radon daughter element by a high-efficiency filter, then continuously pumped into a measurement chamber and discharged to the outside; new daughter element 218Po generated by radon decay in the measurement chamber is adsorbed to the surface of a semiconductor detector under the action of strong electric field, electric signals, which are generated by high energy alpha particles released by the further decay of the 218Po, is subjected to energy identification and then counted to obtain the concentration of the 218Po so as to obtain radon concentration; and the data of radon concentration obtained by measurement is then calculated by applying a specific algorithm, thus the change of radon concentration can be rapidly measured.

Disclosed is a method for measuring 222Rn (radon) and 220Rn daughters in the air by means of an alpha disperse spectroscopy. The method includes collecting radon daughters in the air on a filter film by an air sampling pump, and measuring alpha radioactivity on the filter film by means of the alpha energy disperse spectroscopy. During measuring in short measuring period, measuring period is 2-20 minutes, the number of periods is larger than or equal to three, the number of 222Rn and 220Rn daughters on the filter film at the starting measuring time can be calculated by means of counts of different characteristic peaks of various measuring periods, and concentration of the 222Rn and 220Rn daughters in the air can be reasoned. During measuring in long measuring period, the number of measuring periods is two, both the two measuring periods are 30-300 minutes, the number of 222Rn and 220Rn daughters on the filter film at the starting measuring time can be calculated by means of counts of different characteristic peaks of the two measuring periods, and concentration of the 222Rn and 220Rn daughters in the air can be reasoned.

The invention discloses an alpha energy spectrum measuring method of radon in soil based on a static diffusion and electrostatic adsorption principle of the radon in soil, which comprises the following steps: (A) during measuring, burying a radon daughter electrostatic adsorption device in soil for a period of time, and then taking the radon daughter electrostatic adsorption device out and using an alpha energy spectrum measuring device to measure adsorbed radon daughters; (B) using a high-voltage electrostatic charging device to charge the radon daughter electrostatic adsorption device so as to enable the radon daughter electrostatic adsorption device to have high-voltage static electricity; (C) using an alpha energy spectrum measuring and data managing device to measure the alpha energy spectrum information of the adsorbed radon daughters of the radon daughter electrostatic adsorption device and concentratively managing the data; and (D) using a computer software analysis system to detailedly analyze the measuring data. The method can overcome the defects of the prior measuring method of the radon in soil, solve the problems of low soil radon measurement efficiency, precision, accuracy and reliability, and the like, indirectly measure the radon in soil by measuring nuclides of the radon daughters in soil, overcome the influences of thoron and meet the urgent requirement on the measurement of the radon the soil of the geological survey field and the environmental evaluation field at present.

The invention relates to a method for rapidly measuring 222Rn and 220Rn daughter concentration in air in terms of an alpha general count. An air sampling pump is utilized to collect radon daughters in the air to a filtering membrane, an alpha disintegration total count on the filtering membrane is measured, and therefore air concentration of the radon daughters is calculated. Two kinds of measuring periods exist, namely a short-time interval measuring period and a long-time interval measuring period. When a short-time interval t is taken as the measuring period, data larger or equal to six measuring periods are utilized and nonlinear fitting or the least square method is utilized so as to obtain 222Rn and 220Rn daughter activity on the filtering membrane at the beginning measurement. When long-time intervals, namely t1, t2, t3, t4, t5 and t6 are taken as measuring periods which are 6 in number, the 222Rn and 220Rn daughter activity on the filtering membrane at the beginning measurement can also be obtained. The radioactive decay law and the accumulation law of the 222Rn and 220Rn daughters on the filtering membrane in the sampling process are utilized, and therefore the 222Rn and 220Rn daughter concentration in the air can be obtained in a backstepping mode.

The present invention discloses an accurate calibration method for an alpha-spectrometry peak overlap correction factor of a radon daughter measuring instrument. A radon daughter measuring instrument samples from <220>Rn daughter measurement environment and stands, and then a channel value LV1, corresponding to an upper threshold of a <222>Rn daughter RaA (<218>Po) 6.0MeV spectrometry peak counting area, of the measuring instrument is calibrated by means of multiple channels. The radon daughter measuring instrument samples from pure <220>Rn daughter environment after refilled with a filter membrane. Alpha particle quantities N11 and N12 in a 6.0 MeV counting area and a 7.69 MeV counting area in the time period of 60-120 min are calculated by using the multiple channels, and a peak overlap factor theta1 is calculated. The radon daughter measuring instrument samples from pure <222>Rn daughter environment after the filter membrane is changed, and then a channel value LV2, corresponding to an upper threshold of a <222>Rn daughter RaC'(<214>Po) 7.69MeV spectrometry peak counting area, of the measuring instrument is calibrated by means of the multiple channels. The radon daughter measuring instrument samples from a <220>Rn chamber after being refilled with a filter membrane, alpha particle quantities N24, N23 and N22 are measured via a multi-channel pulse amplitude analyzer, and peak overlap factors theta2 and theta3 are determined.

The invention provides a radon daughter sampling device on the basis of the high-voltage corona discharge principle. According to the device, the traditional thinking is broken through from a radon daughter sampling mechanism. The device comprises a high-voltage electrode plate, a needle electrode, a sampling plate, a gold silicon surface semiconductor detector, a pre-amplifier, a fan, a sampling device upper cover and a bottom shell. The device is characterized in that a sampling filter membrane is not required, in the sampling process, the detector is not polluted, rapid and continuous measurement can be achieved, the device is small, exquisite in size and convenient to carry, the sampling sensitivity of the device is 4-8 times that of a common electrostatic collection method, and the radon daughter sampling device has the wide application prospect in the environment radon measuring fields of various low backgrounds.

The invention belongs to the field of uranium exploration, and particularly relates to a precession drilling-type activated carbon package gamma spectrum radon measurement method. The method comprises the following steps: a precession-type drill bit, an activated carbon package, a self-sealing transparent plastic bag and a gauze bag are customized; a radon decay daughter region of interest and a thorium decay daughter region of interest on a ground gamma spectrometer are set; the overburden ratio of the ground gamma spectrometer and a radon concentration conversion factor are determined; the activated carbon package is packaged; field data are acquired; and the data are processed and corrected. The method can effectively capture radon in a gas, liquid or particle state in a geogas, a radon decay daughter <214>Bi characteristic energy peak net counting rate is measured, the radon concentration is converted after correction and processing, the tedious operation of the conventional activated carbon radon measurement method is simplified significantly, the radon measurement economic cost is greatly reduced and the radon measurement data reliability is effectively improved.

The invention puts forward an artificial radionuclide dissolvability monitoring method and apparatus. The method comprises the following steps: according pulse signals detected by a semiconductor detector, a 214Bi-214Po coincidence event is extracted; the pulse signals comprise alpha pulse signals and beta pulse signals, and artificial radionuclide concentration is calculated according to the pulse signals detected by the semiconductor detector and the extracted 214Bi-214Po coincidence event. Via use of the artificial radionuclide dissolvability monitoring method and apparatus provided in the invention, effects exerted on artificial radionuclide aerosol measurement by 214Bi-214Po can be eliminated at presence of radon and a radon daughter background, and measurement efficiency can be improved.

The invention discloses a radon monitor, comprising a collecting part, a detecting part and a computation processing part. The collecting part comprises a detecting room; the detecting part comprises a silicon detector and an amplifier; the silicon detector is arranged on the inner wall of the detecting room; the computation processing part comprises a data input interface, a data processor, a memory, a display and a keyboard, wherein the data input interface is connected with the detecting part, the data processor is connected with the data input interface; and the memory, the display and the keyboard are connected with the data processor; the silicon detector detects the content of radon and radon daughter in air which enters the detecting room and transmits a detecting signal to the amplifier; and the amplifier transmits the detecting signal to the computation processing part. The invention adopts the silicon detector and sets a high-pressure collecting electrode so as to improve the collecting efficiency of the radon and the detection sensitivity and accuracy of apparatus. The radon monitor has simple structure and low cost, is easy for operation and convenient for carrying, and can be widely used for continuously and automatically detecting the radon of various residential buildings.

The invention provides a radon daughter pollution recovery correction method in the radon measurement of radon daughter electrostatic adsorption, and the method specifically comprises the steps: S1, enabling a testing system to automatically record a current measurement completion moment, and automatically storing a current Po218 measurement value; S2, cutting off high-voltage static, releasing radon in a mode of ohmic discharging and the high-voltage static of the surface of a daughter collection cavity; S3, starting a sucking pump, and automatically flushing the radon and the daughter collection cavity through fresh air according to the set flushing time; S4, starting the high-voltage static, and switching to a next measurement operation; S5, automatically recording the differences t1 and t2 between the start and end time of the current moment and the end time of the former measurement; S6, calculating the residual Po218 value B1 of the surface of a detector through a formula (shownin the description), and removing the residual Po218 value B1 in a new measurement value. The method provided by the invention can achieve the quick removal of a Po218 pollution value attached to thedetector, and achieve the purpose of the quick recovery of the detection system after pollution.

The invention discloses a synchronous measurement and dose rate evaluation method for radon and a radon daughter. According to the method, detection equipment is used for conducting synchronous measurement and dose rate evaluation on the radon and the radon daughter, the detection equipment comprises a radon daughter measurement unit, a radon measurement unit and an electronics system, and the radon daughter measurement unit is composed of a cyclone separator, an electromagnetic valve and a radon daughter sampling chamber; a first alpha detector, an ultra-filtration membrane stepper and an ultra-filtration membrane which is arranged on the ultra-filtration membrane stepper are arranged in the radon daughter sampling chamber, the radon measurement unit is composed of a scintillation chamberand a sampling pump, and a second alpha detector is arranged in the scintillation chamber; the first alpha detector is electrically connected with the second alpha detector through the electronics system. According to the synchronous measurement and dose rate evaluation method for the radon and the radon daughter, the radon measurement application environment is enlarged, the measurement precision is improved, multiple parameters are simultaneously acquired, and the measurement efficiency is further improved.

The invention discloses a radon removal purification method and device, and aims to solve the problems that uncombined radon daughters in air are difficult to effectively remove and the overall treatment efficiency is not ideal in the prior art. The radon removal purification method comprises the following steps: firstly, filtering radon daughters carried by aerosol from input air to be purified to obtain primarily purified air; then drying the primarily purified air to remove moisture; and then using the cold trap segregation and low-temperature adsorption principle for conducting physical refrigeration and adsorption on the dried air, so as to obtain fully purified air. According to the invention, the traditional radon removal and purification design thought is broken through, the physical properties of radon are utilized, non-combined radon with larger radiation dose pollution is removed through cold trap segregation and low-temperature adsorption, and meanwhile, combined radon daughters are filtered through dust removal, so that radon in air is removed more quickly and efficiently.

The invention discloses a radon measuring device and a radon measuring method, and particularly relates to the field of radon concentration measurement, and the radon measuring device comprises an instrument box body, and a radon measuring mechanism and a radon measuring system which are installed in the instrument box body; the radon measuring mechanism comprises a radon measuring chamber, a radon daughter filter, a drying pipe, an electromagnetic valve A, an electromagnetic valve B, a flowmeter and a sampling pump; and the radon measuring system comprises an amplifier, a threshold discrimination circuit, a counting circuit, a control circuit and a power supply circuit. To-be-measured air after radon daughters are filtered is collected into a radon measuring chamber through a sampling pump, radon in the measuring chamber is decayed into the radon daughters, [alpha] radioactive decay on a filter membrane is measured, multi-time-period measurement is conducted, the radon daughter concentration is calculated through adoption of a weighted least square method, The whole measuring device can measure radon and radon daughters at the same time, the measuring precision is high, and two measuring modes including a standard measuring mode and a rapid measuring mode are adopted, one mode achieves high-precision measurement, and the other mode achieves rapid measurement.

The invention relates to a fast detection device and method for the radon decay based on radon daughter suppression, and relates to the technical field of nuclear radiation detection. The fast detection device for radon decay based on radon daughter suppression comprises a first scintillation chamber and a second scintillation chamber, wherein both the first scintillation chamber and the second scintillation chamber include a plurality of cylindrical and light-proof shells, the inner diameter of the shells of the first scintillation chamber is less than the inner diameter of the shells of thesecond scintillation chamber, the shells are laminated from the bottom up and sequentially connected, the inner cavity of each shell is internally provided with a plurality of partition plates, and the partition plate divides the inner cavity of the shell into a plurality of fan-shaped chambers. The invention mainly improves the existing radon measurement method on the principle and methodology for radon detection. According to the invention, a fast radon detection model is constructed based on the detection radon decay, the influence of radon daughters on the detection radon is suppressed toa great extent by using electrostatic collection, filter membrane filtering and the scintillation chambers of the specific structure, and <222>Rn and <220>Rn are effectively distinguished in one measurement through the scintillation chambers of different geometric sizes.

The invention discloses an air radon daughter removing method and a device for realizing the method. The method comprises the following steps: (10) single-area electrostatic field radon removal: radon-contained air flows through a honeycomb-shaped electrostatic field to remove one part of radon daughters; and (20) electrostatic fiber radon removal: the air flows through an electrostatic fiber filter to remove the remained radon daughters after passing through the honeycomb-shaped electrostatic field. The device comprises an air flue (1), and the honeycomb-shaped electrostatic field (2) and the electrostatic fiber filter (3) arranged in the air flue (1) in sequence in the airflow direction; and the honeycomb-shaped electrostatic field (2) and the electrostatic fiber filter (3) are both connected with the inner wall of the air flue (1) in a closed manner. The air radon daughter removing method and device are compact and simple in structure, are energy-saved, and are high in efficiency.

The invention discloses a radon daughter potential calculation method based on a high voltage corona sampling method. A technical scheme of the invention is characterized by firstly, using the high voltage corona sampling method to collect radon daughters; then using a total alpha measurement system to measure a sampling sheet; according to a formula given in the invention, solving a time factor; and finally acquiring a radon daughter potential concentration. Simultaneously, the invention provides calculation steps of a comparison method used for a key parameter scale coefficient. The calculation method provided in the invention is the radon daughter potential concentration calculation method based on the high voltage corona sampling method and the method is high-efficiency, flexible and easy to realize. And the method can be popularized to other radon daughter potential concentration measuring instruments.

The invention belongs to the nuclear radiation monitoring technology field and relates to a radon reduction system for a low natural radioactivity level measuring chamber. The radon reduction system comprises the measurement chamber, shielding bodies, a shielding door, air intake equipment, a filtering adsorption device, a ventilation duct, an air inlet and an air outlet, wherein four side walls, the top surface and the bottom surface of the measurement chamber are provided with the shielding bodies, one side wall is provided with the shielding door, ventilation of the measurement chamber is realized by the external air intake equipment through the ventilation duct and the air inlet of which the tail end is connected with the measurement chamber, the air outlet is arranged in the measurement chamber and is used for carrying out air exhaust outwards, air input of the air inlet is greater than air output of the air outlet, and the filtering adsorption device is arranged on the ventilation duct. The radon reduction system is advantaged in that radon concentration and radon daughter concentration can be effectively reduced.

An environmental radon gas measuring method and measuring instrument belong to the technical field of gas detecting methods and instruments. The technical problem to be solved is to provide a detection method and detection instrument that can quickly measure radon concentration and balance factor simultaneously, have large measurement range, wide applicability, high accuracy, and are convenient to use. Its technical solution is: the sampler is supported at the sampling position, the sampling piece composed of double-layer film is placed on the electrode plate, the electrode plate is connected to negative high voltage, the sampling piece absorbs the radon progeny in the indoor air space, and then the The sampling piece is placed in the sample tray between the upper and lower detectors in the host, and the measurement is started. The calculation software installed in the instrument automatically calculates the air radon concentration and balance factor at the sampling position. The sampling part of the tester is composed of film sampling sheet, electrode plate, cable, high voltage power supply, etc. The sample processing part is composed of detector, amplifier circuit, pulse analyzer, microprocessor, memory, decoder, latch and so on.

The invention discloses a method for rapidly measuring radon concentration by zero-order approximation, comprising measurement and calculation. At first, a radon measurement instrument is enabled to work under a scale mode, radon concentration is reversely deduced by using the counting of a long-time 218Po peak in a standardized radon chamber to obtain a scale factor, which is therefore equivalent to an RAD7 radon measurement instrument working under a sniff mode; the radon measurement instrument is then switched to work under a zero-order approximation mode, measurement cycle and cycle times are set, and after the radon measurement instrument is started up, the air outside is subjected to the filtration of radon daughter element by a high-efficiency filter, then continuously pumped into a measurement chamber and discharged to the outside; new daughter element 218Po generated by radon decay in the measurement chamber is adsorbed to the surface of a semiconductor detector under the action of strong electric field, electric signals, which are generated by high energy alpha particles released by the further decay of the 218Po, is subjected to energy identification and then counted to obtain the concentration of the 218Po so as to obtain radon concentration; and the data of radon concentration obtained by measurement is then calculated by applying a specific algorithm, thus the change of radon concentration can be rapidly measured.

The invention discloses a radon measurement dehumidification method, and particularly relates to the field of air radon concentration measurement, and the method comprises the following specific steps: radon-containing air passes through a radon daughter filter, a flowmeter, a first solenoid valve, a radon measurement chamber, a pump and a second solenoid valve, and is finally discharged into the atmospheric environment; and the air in the radon measuring chamber is completely replaced by air with the same radon concentration as the external air, then the air in the radon measuring chamber forms internal circulation through the drying pipe, moisture in the air is absorbed by the drying pipe and becomes dry radon-containing air with extremely low humidity, dehumidification of an air sample to be measured is completed, and measurement of the sample is started. On the premise that radon concentration measurement is not affected, the same drying effect can be achieved when the using amount of the drying agent is one third of that of a traditional method, the using amount of the drying agent is greatly reduced, the size and the weight of a radon measuring instrument are reduced, and the portability and the measuring efficiency of the radon measuring instrument are effectively improved.

The invention discloses a physical adsorption heat-resistant radioactive contamination purification type monitoring device which comprises a bottom plate, a flow dividing box, a radiation treatment cylinder, a concentration aggregation type radioactive substance heat absorption treatment mechanism and a split flow type conductive adsorption detection mechanism, the flow dividing box is arranged on the upper wall of one end of the bottom plate, and the flow dividing box is arranged on the lower wall of the other end of the bottom plate; the radiation treatment cylinder is arranged on the upper wall of one end, far away from the shunting box, of the bottom plate, the concentration aggregation type radioactive substance heat absorption treatment mechanism is arranged on the radiation treatment cylinder, and the split flow type conductive adsorption detection mechanism is arranged on the concentration aggregation type radioactive substance heat absorption treatment mechanism. The invention belongs to the technical field of pollution monitoring equipment, and particularly relates to physical adsorption heat-resistant radioactive pollution purification type monitoring equipment. The physical adsorption heat-resistant radioactive contamination purification type monitoring equipment provided by the invention can perform flow adsorption measurement on radon daughters and can perform low-temperature continuous adsorption on radon gas.

The invention relates to the technical field of radon measurement, and provides a radon exhalation rate measuring instrument which comprises a radon exhalation cover, a radon measurement chamber and a detector. The radon measurement chamber is arranged in the radon exhalation cover, a collection electric field is formed because of a voltage difference between the detector and the radon measurement chamber, and radon daughters generated after radon decay carry positive charges and tend to one side with low potential energy of the electric field, so that the radon exhalation rate of the surface of an object to be measured in a natural state is measured.

The invention belongs to the field of radioactive detection equipment, and particularly relates to a gas drying device with a radon daughter filtering function, the gas drying device comprises a gas inlet chamber, a dust filtering bin, a drying pipe and a radon daughter filtering device, the gas inlet chamber is detachably connected with the dust filtering bin, the gas inlet chamber is detachably connected with the drying pipe, and the drying pipe is detachably connected with the radon daughter filtering device. The device integrates the radon daughter filtering function and the gas drying function, the overall structural design is light and easy to carry, interfaces are unified, gas circuit connection is simple, and the device is suitable for a common environment radon measuring instrument.

The invention discloses an equilibrium equivalent radon concentration calculating method based on a high-voltage corona sampling method. The technical scheme brought forward by the invention is as follows: first of all, a radon daughter element is sampled by use of the high-voltage corona sampling method, then alpha net areas which are corresponding to RaA(<218>Po) and RaC'(<214>Po) within a time period of ti=120 seconds to ti=320 seconds and a time period of ti=1200 seconds to ti=1600 seconds are measured by use of an alpha energy spectrum measuring system, and then an equilibrium equivalent radon concentration is solved by use of a formula. At the same time, the invention provides steps for solving a key parameter scale coefficient k by use of a comparison method. According to the invention, the equilibrium equivalent radon concentration calculating method based on the high-voltage corona sampling method is a calculation method which is accurate, highly efficient and easy to realize. The method can also be popularized for application in other radon daughter element measuring methods.

Disclosed is a method for measuring 222Rn (radon) and 220Rn daughters in the air by means of an alpha disperse spectroscopy. The method includes collecting radon daughters in the air on a filter film by an air sampling pump, and measuring alpha radioactivity on the filter film by means of the alpha energy disperse spectroscopy. During measuring in short measuring period, measuring period is 2-20 minutes, the number of periods is larger than or equal to three, the number of 222Rn and 220Rn daughters on the filter film at the starting measuring time can be calculated by means of counts of different characteristic peaks of various measuring periods, and concentration of the 222Rn and 220Rn daughters in the air can be reasoned. During measuring in long measuring period, the number of measuring periods is two, both the two measuring periods are 30-300 minutes, the number of 222Rn and 220Rn daughters on the filter film at the starting measuring time can be calculated by means of counts of different characteristic peaks of the two measuring periods, and concentration of the 222Rn and 220Rn daughters in the air can be reasoned.

The invention relates to a fast detection device and method for the radon decay based on radon daughter suppression, and relates to the technical field of nuclear radiation detection. The fast detection device for radon decay based on radon daughter suppression comprises a first scintillation chamber and a second scintillation chamber, wherein both the first scintillation chamber and the second scintillation chamber include a plurality of cylindrical and light-proof shells, the inner diameter of the shells of the first scintillation chamber is less than the inner diameter of the shells of thesecond scintillation chamber, the shells are laminated from the bottom up and sequentially connected, the inner cavity of each shell is internally provided with a plurality of partition plates, and the partition plate divides the inner cavity of the shell into a plurality of fan-shaped chambers. The invention mainly improves the existing radon measurement method on the principle and methodology for radon detection. According to the invention, a fast radon detection model is constructed based on the detection radon decay, the influence of radon daughters on the detection radon is suppressed toa great extent by using electrostatic collection, filter membrane filtering and the scintillation chambers of the specific structure, and <222>Rn and <220>Rn are effectively distinguished in one measurement through the scintillation chambers of different geometric sizes.

The invention discloses a method for eliminating influence of radon and radon daughters upon polypropylene process and a radioactive instrument. The method is aimed at solving problems arising from conventional polypropylene process. A great discrepancy between display of the instrument and actual material occurring in case of sudden abnormity for alarm of continuous material level and high-and-low material level is avoided. Even when material is present in the conventional reaction kettle, zero material level or negative material level is displayed by a level gage. In order to solve the above problems, the method is characterized in that the outer wall of a detector is wrapped in a layer of lead sheath; and a 6mCicaesium-137 radioactive source is adopted by a radioactive source. The method for eliminating influence of radon and radon daughters upon polypropylene process and the radioactive instrument has following beneficial effects: the 6mCicaesium-137 radioactive source is adopted so as to reduce the proportion of gamma rays emitted from radon and radon daughters received by a detector and a measurement condition for the level gauge is satisfied; by protecting the outer wall of the detector with lead, environment interference is reduced and high pressure of the instrument and activity of the radioactive source are improved in order to increase pulse received by the instrument, prolong delay time of the instrument and prevent the environment influence upon the instrument from generating fluctuation; and when material is not fed, the zero point in the thermal state of the instrument is calibrated by increasing temperature and pressure

A method is presented for collecting and removing radon from a confined area, a storage box or articles of clothing. The method includes collecting radon from the confined area or around a storage box via at least one collector, connecting each of a plurality of radon adsorbers to a corresponding power supply or power source such as a battery, capacitor, fuel cell, etc. diverting, via a plurality of valves, the collected radon or radon daughters through one or more of the plurality of radon adsorbers, and receiving, via a plurality of radon storage units, radon or radon daughters held by the plurality of radon adsorbers for a predetermined period of time.