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Leaders in professional radon instrumentation and analysis solutions |
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DURRIDGE offers a variety of provides built around our flagship radon detector, the RAD7. Each is explained in detail below. |
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Electronic radon detector with real-time monitoring and spectral analysis |
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The DURRIDGE RAD7 is a truly versatile radon detector of mature and yet still state-of-the-art design. Its specifications match or exceed those of the most expensive radon measurement devices in the world. At the same time, it incorporates a number of exclusive features that are found in no other radon detector, regardless of price. Incredibly, the RAD7 is affordable. The RAD7 is a sophisticated measuring instrument widely used in laboratories and research work around the globe, by radon testers, mitigators and home inspectors, in mines and deserts, on the ocean and up volcanoes, at extremes of temperature. The RAD7 is also the simplest computer-driven electronic detector to use, with pre-programmed set-ups for common tasks. It's built to withstand everyday use in the field. A rugged, handsome case encloses the detector, which is self-contained and self-sufficient. The RAD7 comes complete, with a built-in air pump, rechargeable batteries, and a wireless infrared printer. The printer can be left in your office or your car, when desired, and the detector will collect data and store it for later printing or downloading to a PC. The RAD7 is a Sniffer that uses the 3-minute alpha decay of a radon daughter, without interference from other radiations, and the instantaneous alpha decay of a thoron daughter. The RAD7 sniffs out entry points and radon gushers and recovers in minutes from high radon exposures. The RAD7 is also a Continuous Monitor that measures the EPA action level of 4 pCi/L, with 10% standard deviation, in one hour. At the end of each run, the detector prints out a complete report. RAD7 Advantages
Convenience and Ease of Use
Security and Flexibility
Expandability and Value
Operating the RAD7 The RAD7 is remarkably easy to use. It's ready to operate from the moment you turn it on. The first thing you will see is the Setup Review, which displays the current settings. This allows you to check that your machine is set up the way you want it for your intended use. Now you and your RAD7 are ready to go to work. The machine is preset for a 1- or 2-day test... or you can preset for your particular job that day. When you arrive on site, just push the buttons and the test runs automatically. A RAD7 exclusive feature is "Auto" mode. This starts a test in Sniff mode for quick response, a base-line reading. After 3 hours it automatically switches to "Normal" mode for the remainder of the test, assuring statistical precision. You can leave your RAD7 for a 24-hour, 48-hour or any-hour test, knowing that the measurements will be correct, thanks to the "Test Lock" command, which locks the machine until you return. The display shows "DURRIDGE RAD7", the test continues, and no amount of tampering - intentional or unintentional - can influence it. |
RAD7 electronic radon detector Alpha Energy Spectrum |
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RAD7 Technical Specifications Functionality:
Technical Specifications:
Physical Specifications:
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Radon In Water Accessory for the RAD7 |
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The RAD H2O is an accessory for the RAD7 that enables you to measure radon in water over a concentration range of from less than 10 pCi/L to greater than 105pCi/L. By diluting your sample, or by waiting for sample decay, you can extend the upper range to any concentration. The equipment is portable and battery operated, and the measurement is fast. You can have an accurate reading of radon in water within an hour of taking the sample. The RAD H2O gives results after 30 minutes analysis with a sensitivity that matches or exceeds that of liquid scintillation methods. The method is simple and straightforward. There are no harmful chemicals to use. Once the procedure becomes familiar and well understood it will produce accurate results with minimal effort. By taking two simultaneous samples, analyzing one immediately, waiting a week or more and then analyzing the other, the radium (226Ra) content of the water may be calculated. Product Highlights
Configuration A vial containing a water sample is set up in a closed air loop with the RAD7. The RAD7 pump operates automatically for five minutes to aerate the sample, distributing the radon that was in the water throughout the loop. The RAD7 waits a further five minutes while the 218Po count rate approaches equilibrium and then counts for four five-minute cycles. The radon concentration in the water is calculated directly. Documentation
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RAD H2O connected to RAD7 (not included)
RAD H2O Configuration Diagram |
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Continuous Radon in Water Accessory for RAD7 |
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The RAD AQUA is an accessory for the DURRIDGE RAD7 radon detector that is used to bring the radon concentration in a closed air loop into equilibrium with the radon concentration in a flow-through water supply. It consists of a spray chamber, called an "exchanger", that brings the air and water into equilibrium. The radon in the air is monitored continuously by the RAD7. The partition coefficient (the ratio of radon concentration in the water to that in the air at equilibrium) is determined by the temperature at the air/water interface. This temperature is measured with a temperature probe inserted into the exchanger. At typical room temperature the coefficient is about 0.25. That means the concentration of radon in the air is four times higher than in the water. As a result, the system's sensitivity to radon in water is four times higher than the sensitivity to radon in air. It takes time for the water to deliver radon to the air loop and for the RAD7 to respond to the changed radon concentration. With optimum configuration the response time of the system may be reduced to less than half an hour. Product Highlights
How it Works Water passes continuously through the RAD AQUA exchanger. Air flows in a closed loop through the exchanger and through the RAD7. Radon in the air comes into equilibrium with radon in the water. From the radon concentration in the air and the temperature of the air/water interface, the radon concentration in the water is determined. This is the fastest, most sensitive method of measuring radon in water, and it can monitor both radon and thoron levels continuously. Documentation
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RAD AQUA Assembly |
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Slow Response Monitoring of Radon in Water |
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The DURRIDGE Water Probe is used to collect radon samples from large bodies of water. The probe consists of a semi-permeable membrane tube mounted on an open wire frame. The tube is placed in a closed loop with the RAD7. When the probe is lowered into water, radon passes through the membrane until the radon concentration in the air in the loop is in equilibrium with the water. The equilibrium ratio of radon in the air to radon in the water is determined by the temperature, which must be measured. The probe has the same high sensitivity as the RAD AQUA. As such it can be used to monitor the radon concentration at a specified depth in open water. The probe has an advantage in that it does not need a pump for the water. It will, however, take more than two hours to make a spot measurement or to respond to a step-change in radon concentration. It is important that there be some flow of water around and through the device as it will remove radon from the water in its vicinity as the radon passes into the membrane tubing. To monitor a water supply, the probe may be placed in a container with the incoming water released at the bottom of the container and overflowing or exiting through an outlet at the top. The water in the container should be completely refreshed with incoming water at least twice an hour. Purchasing
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Water probe outer view
Water probe internal structure |
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In-Ground Radon Detection |
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When measuring radon underground, it is essential to collect samples without exposing them to the outside air. DURRIDGE offers two heavy-duty soil probes for this purpose: the durable and easy to use AMS Stainless Steel Soil Gas Probe, and the regular Steel Soil Gas Probe. Designed to be simple and effective, DURRIDGE's Soil Gas Probes consist of a hollow steel tube with a collar and NPT thread at the top. An included drive rod slides down the inside of the tube and penetrates the ground. Also supplied with the probe is a pilot solid steel rod 3/8” diameter to make a pilot hole for the probe. The only necessary equipment, besides the RAD7 itself, is a self-grip wrench, a 5/8" open or adjustable wrench, hammer and teflon tape. Probe Placement and Connection DURRIDGE's Soil Gas Probes operate anywhere above the water table, preferably in soil containing few stones. The pilot rod is hammered most of the way to the depth required, then removed and replaced with the drive rod inside the probe. Once it has been hammered down to the required depth, the drive rod is removed, creating a channel through which soil gas may flow upward. The soil probe may be connected to the RAD7 by either pushing the plug-in hose connector into the probe, or screwing on the NPT hose connector. Tamping down the soil around the probe prevents the leakage of fresh air into the sample acquisition path or down the outside of the probe to the sampling point. The Soil Gas Probe may be used in conjunction with the laboratory drying unit and the DRYSTIK, using the supplied plastic tubing. Modes of Operation There are three modes of soil gas measurement. One is by obtaining a sample in GRAB mode; another by continuous monitoring using the standard protocol; and the third by operating the RAD7 in THORON mode. If necessary, the soil gas sample can be pumped out of the ground by a sampling pump, and fed to a Tedlar sample bag for later analysis by the RAD7. Continuous monitoring is a simpler method of measuring the soil gas radon concentration and provides time resolution in the event that the weather changes. In this protocol, the RAD7 will pump for the first five minutes of every half-hour cycle, and then for only one minute in every five, once the relative humidity drops below 10%. After two hours of continuous monitoring, this would amount to 20 L, which would come from a sphere around the sampling point of around 6" (15 cm) radius. Less porous soils would have a slower flow rate, so the volume of soil gas sampled would be less. Thoron protocol uses 5-minute cycles, during which the pump is run continuously, to accommodate the short half-life of thoron. This mode produces an approximate indication of underground thoron. Documentation
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Soil Gas Probe configuration
Regular Steel Soil Gas Probe close-up |
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Humidity Exchanger to Extend Desiccant Life Span |
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The DURRIDGE DRYSTIK transfers humidity in incoming air to the stream of dry air being pumped out of the RAD7. This means that any air being sent through a drying unit on its way to the RAD7 will have already lost most of its moisture, greatly extending the life of the desiccant in the drying unit. The DURRIDGE DRYSTIK is available in two models: the Active DRYSTIK and the Passive DRYSTIK. The Active model comes bundled in an enclosure containing a built-in pump, while the Passive model relies exclusively on the RAD7's internal pump. Each model is available with three lengths of tubing, with the greater lengths permitting increased preservation of desiccant. In typical conditions, the 12" Passive DRYSTIK will preserve a container of desiccant for two months of continuous use, a significant improvement over its standard useful life span of 10 days. The 48" Active DRYSTIK, by comparison, will preserve the desiccant for over three months. DURRIDGE also offers a premium 144" option. Both the Passive and the Active DRYSTIK models operate on a principle involving two tubes, one inside the other. The inner tube is made of NAFION, a Teflon based material that permits the movement of water molecules, while blocking air and radon. The air sample flows along the inner tube on its way to a drying unit (not included), while the space around the inner tube is purged with dry air coming from the outlet of the RAD7. DRYSTIK Configuration The 12-inch Passive DRYSTIK consists of open tubing, with a wand-like handle that can be aimed at possible radon sources. One end of the tubing is attached to the inlet of the drying unit. The longest piece of tubing is attached directly to the outlet hose connection on the RAD7. The shorter lengths of tubing at the other end of the DRYSTIK are positioned to inhibit the diffusion of moist ambient air into the tubes of the DRYSTIK. The two air streams flow in opposite directions, so that the sample air leaves the DRYSTIK from the same end that the dry air from the RAD7 enters. The 12-inch Passive DRYSTIK is unique in that it is the only model with exposed tubing. All other DRYSTIK models are housed in a compact enclosure. It is easy to set up these DRYSTIKs, as shown in the diagram below. Summary of Benefits The DRYSTIK enables users to enjoy the full capabilities provided by the superior RAD7 technology, with its rapid response and recovery, vanishingly small background, thoron specific sniffing, and radon-in-water accessories, with the need to replace and/or regenerate the desiccant only after a long period. The cost of replacing used desiccant with new Drierite becomes insignificant. With a pump upstream and a needle valve downstream of the NAFION tube, compressing the air inside the tube, the Active DRYSTIK works regeneratively, and can even eliminate the need for desiccant altogether. Media
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Active DRYSTIK Enclosure 
12-inch Passive DRYSTIK with NAFION Tube |
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Accessory for Active DRYSTIK and Soil Probe |
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Monitoring soil gas in the long term, for geotechnical and earthquake studies, is likely to dilute the soil gas sample with fresh air diffused down from the surface. The DURRIDGE Duty Cycle Controller can control the 12V supply to an Active DRYSTIK, with a duty cycle anywhere from 100% to less than 1%. This means that the average flow rate can be carefully controlled to eliminate dilution of the sample and enable soil gas sampling to continue indefinitely. Functionality The DURRIDGE Duty Cycle Controller controls the on and off time of a DC voltage powered device, resulting in lower power usage, lower consumption of consumable resources, and, in the case of a device with a pump, lower average flow rate. The DURRIDGE Duty Cycle Controller accepts a continually-on supply voltage between 9-15 VDC and converts it to a modulated square wave signal. The Duty Cycle Controller has an ON time in each cycle of 3 seconds. The OFF time in the cycle may be varied from zero to 1,000 seconds or fully off. Side benefits to reducing the flow rate include reducing wear on the Active DRYSTIK pump and increasing the life of the desiccant. The Duty Cycle Controller can also control the power to any other 12V device, such as a sampling pump, whose current draw is not more than 1A. Thus a sampling pump may be set, by the Duty Cycle Controller, to pump for three seconds once every minute. Documentation
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Increase the range of the RAD7 in high radon areas |
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The Range Extender mixes fresh air with sample air to reduce the concentration of radon in the air fed to the RAD7 radon detector by an order of a magnitude, greatly increasing its effective range. The extender consists of two parallel capillary tubes joined at one end to the outlet hose connector. Fresh air is fed to the input of one tube while the incident radon sample is fed to the other. A differential pressure sensor across the two tube inputs, with a needle valve for adjustment, is used to ensure that both capillary tubes have the same pressure drop across them. With this system the radon concentration delivered to the RAD7 will be reduced by a factor of 10:1 regardless of the strength and flow velocity of the RAD7 pump. The pump can cycle on and off without affecting the reduction factor. The Range Extender can be used for the measurement of very high radon concentrations in air, in soil gas and in water. It can also be used with any other instrument that has its own pump, for any gas. If used to extend the range of thoron measurement care must be taken to assess and correct for the additional decay of the thoron due to sample acquisition delay. Documentation
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Soil and Hard surface emission detection |
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Two emission chamber accessories are offered for the RAD7 radon detector: one for soil surfaces and one for hard surfaces. The Soil Surface Emission Chamber has a stainless steel skirt around the circumference, to penetrate the soil. The Hard Surface Emission chamber has a flat base with sealant. For soil emission measurements, the skirted chamber may be placed on the ground and stood upon, to push the steel skirt into the dirt. A closed loop measurement may be completed in approximately 30 minutes. Open loop monitoring may be performed continuously, showing diurnal variation of soil emission and allowing the user to obtain as high a precision as desired. For hard surface emission measurements, the chamber without the metal skirt, and with a soft seal instead, may be applied to the surface. Closed and open loop measurements may be made. Closed loop protocol provides a quick and sensitive reading, while open loop offers increased scope for investigating variations in emission due to changes in parameters such as barometric pressure, temperature, relative humidity, and ambient radon concentration. Purchasing
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Soil / Hard Surface Emission Chamber: top view
Hard Surface Emission Chamber: bottom view
Soil Surface Emission Chamber: bottom view
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High Sensitivity Radon In Water Accessory for the RAD7 |
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The BIG BOTTLE RAD H2O is an accessory for the RAD7 that enables users to measure radon in large volumes of water with high sensitivity. Its main function is to analyze 2.5L water samples with high precision and high sensitivity. The lower limit of detection is about 1 pCi/L (37 Bq/m3) radon concentration in the water. The upper limit of detection is 103 pCi/L (3811 Bq/m3). For ranges higher than that, the standard RAD H2O accessory is recommended. The BIG BOTTLE RAD H2O system consists of several components, including the Tubing Set, Support Stand, Glass Bottle, Elastic Clinching Strap, USB Temperature Logger, Hermetically Sealed Thermocouple, and two 2.5 L Glass Bottles. The tubing set includes a check valve, aerating stones, aerator, and bubble trap. A RAD7 is required, as is either a Laboratory Dryer or DRYSTIK. The complete system (excluding the optional Active DRYSTIK), is portable and battery operated, and the measurement is moderately fast. Even for the lowest radon concentrations you can have an accurate reading of radon in the water within two hours of taking the sample. The BIG BOTTLE RAD H2O gives results after 120 minutes of analysis, or less, with a sensitivity that far exceeds that of liquid scintillation methods. The method is simple and straightforward, and there are no harmful chemicals to use. Once the procedure becomes familiar and well understood it will produce accurate results with minimal effort. Media
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BIG BOTTLE RAD H2O Aerator and Temperature Data Logger |
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CO2 Sampling Data Logger |
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The Portable CO2 Sampling Data Logger is designed to log carbon dioxide levels in the air being fed through a RAD7. The sampling allows for elevated ambient temperatures, and relative humidity. Inside the Sampling Data Logger is an optional battery-operated micro-pump connected to two tubing ports on the side of the unit. The unit is designed to automatically turn itself on (15 seconds up to once every 18 hours), draw gas for a programmable period from the inlet port and expelling it from the discharge port, make a measurement and store the value internally with time stamp. The data is retrieved form the unit via USB connection to a computer running the downloadable DAS software. The battery-operated, portable Sampling Data Logger comes in five models: 1%, 5%, 30%, 65% and 100% CO2. All models include a data cable for retrieving accumulated measurements. A backlit LCD that changes color according to CO2 levels and is programmable. Filters, fittings, tubing and auxiliary international power supply. Specifications
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