DURRIDGE offers a variety of accessories for the RAD7 radon detector. Each is explained in detail below.

Range Extender – Increase the range of the RAD7 in high radon areas
CO2 Logger – CO2 Sampling Data Logger
Cool Trap – Remove moisture from air entering the DRYSTIK and RAD7
Indoor Faucet Connector – Adaptor for taking tap water samples
Natural Rock Sample – Monitor RAD7 performance up to once per month
Relay Box – Accessory for issuing alerts and controlling the RAD7 operating environment
Serial to Bluetooth Adaptor – Adaptor for communicating wirelessly with the RAD7 from a computer
USB to Serial Adaptor Cable – Cable for connecting the RAD7 to a computer
Water Switch – Prevent water from entering the DRYSTIK and other sensitive devices

Range Extender

$1,353.00Add to order

Increase the range of the RAD7 in high radon areas

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.

Physical Specifications
Range Extender Shipping Dimensions 12″ x 12″ x 10″ (30 cm x 30 cm x 25 cm)
Range Extender Shipping Weight 4 pounds (1.8 kg)

DURRIDGE Range Extender

Range Extender


Range Extender User’s Manual (PDF)

CO2 Logger
Measure CO2 levels in the air entering the RAD7

The portable CO2 Logger is designed to log carbon dioxide levels in the air being fed through a RAD7. The device works at elevated ambient temperatures and relative humidity levels.

The CO2 Data Logger features custom tightened seals on its two tubing ports. The device itself does not contain a built-in pump; instead air is drawn in through the device by the RAD7’s internal pump. The CO2 Data Logger stores CO2 readings internally with a time stamp, and the data is retrieved from the unit via USB connection to a computer running the downloadable data acquisition software.

The battery-operated, portable CO2 Data Logger comes in four models, for measuring CO2 concentrations of up to 1%, 5%, 30%, and 100%, respectively. All models include a data cable for retrieving accumulated measurements. A programmable backlit LCD changes color according to CO2 levels. The package includes filters, fittings, tubing, and an auxiliary international power supply.

  • CO2 Measurement: non-dispersive infrared (NDIR).
  • Sampling Method: Tube sampling
  • 15,000 measurement capacity
  • Measurement interval: 15 second to 18 hours.
  • Sensor Life Expectancy: > 15 years
  • Calibration certificate included
  • No maintenance required
  • Size: 5.75×5.6×1.3in (146×91×33mm)
  • Tubing sizes: 3/32 or 1/8″
  • Measurement Ranges:
    1% (0-10,000 ppm)

    $1,250.00Add to order

    5% (0-50,000 ppm)

    $1,250.00Add to order

    30% (0-300,000ppm)

    $1,310.00Add to order

    100% (0-1,000,000 ppm)

    $1,443.00Add to order

  • LED displays CO in PPM for 1%, 5% and in percentage XX.YY% for 30%, 100%
  • 4 AA batteries (not included)
  • International wall power supply (included)
Included Accessories
  • USB A to USB mini cable
  • 1/8-inch tubing 10 feet
  • International wall mount power supply
  • Moisture trap
  • Particulate and hydrophobic filters
  • Assorted tubing fittings

DURRIDGE CO2 Sampling Data Logger

CO2 Sampling Data Logger


CO2 Logger Manual (PDF, CO2Meter.com)

Software Support

Data Acquisition System (DAS) Software (HTML, CO2Meter.com)

Cool Trap
Remove moisture from air entering the DRYSTIK and RAD7

The Cool Trap is a RAD7 accessory that operates under pressure in a vessel of icy water, directing air through a coil of copper tubing. This process creates condensation and removes excess moisture from the air. The Cool Trap operates upstream of the laboratory drying unit, DRYSTIK, or RAD7, to reduce the amount of moisture advancing through each.

Two versions of the Cool Trap are available: the Bucket-Sized Cool Trap and the Mug-Sized Cool Trap. The Mug-Sized Cool Trap is more portable, while the Bucket-Sized Cool Trap offers greater moisture removal due to its longer tubing. Both versions of the Cool Trap have one air inlet tube and two outlet tubes, one for outputting the dried air, and another for draining the condensed water.

Cool Trap Specifications
  Mug Sized Cool Trap Bucket-Sized Cool Trap
Diameter 2.75 in (7.0 cm) 7.50 in (19.1 cm)
Height 5.75 in (14.6 cm) 11.75 in (29.9 cm)
Weight 0.6 lbs (270 g) 3.2 lbs (1.5 kg)
Material Copper Copper

$203.00Add to order

$307.00Add to order

  • DURRIDGE Mug-Sized Cool Trap
    Mug-Sized Cool Trap

    DRYSTIK Configuration with Cool Trap Diagram
    DRYSTIK Configuration with Cool Trap Diagram

  • Cool Trap in Mug
    Cool Trap in Mug

    Bucket Sized Cool Trap Photo
    Bucket Sized Cool Trap


Cool Trap Configuration with DRYSTIK (PDF)
See Section 2.4, High Humidity Conditions

Indoor Faucet Connector

$25.00Add to order

Adaptor for taking tap water samples

For filling RAD H2O vials or bottles, and feeding tap water into the RAD AQUA spray chamber, DURRIDGE offers an Indoor faucet connector manufactured by Claber Inc. It attaches to any indoor straight neck faucet up to 1¼ inch wide. A rubber seal clamps onto the faucet to prevent leaking or spraying, and a convenient quick-click coupler allows for fast and easy hose removal.

Connector Specifications
Construction UV-stabilized ABS Plastic
Maximum Water Temperature 104° F (40° C)
Operating Pressure 14.5 PSI (1 Bar) to 58 PSI (4 Bar)
Leak Pressure 145 PSI (10 Bar)
Maximum Faucet Width 2.75 in (7.0 cm)
Maximum Faucet Height 5.75 in (14.6 cm)
  • DURRIDGE Indoor Faucet Connector
    Indoor Faucet Connector
  • DURRIDGE Indoor Faucet Connector
    Indoor Faucet Connector in use
Natural Rock Sample
Monitor RAD7 performance once each month

The Natural Rock Sample system consists of a 21oz (600g) sample of granite gravel from a stone quarry, normally sold by the truckload as construction material. It is enclosed in a container that, by closing two ball valves, may be completely sealed.

Granite, in general, contains trace amounts of both uranium and thorium that has been in the rock since it was formed, millions if not billions of years ago. Therefore all the progeny of both the uranium and thorium decay chains are fully supported and in full equilibrium down to 226-Ra and 224-Ra.

The rock sample is dry and therefore constitutes a rock-steady emitter of both radon and thoron. It is possible to take advantage of that property to check the performance of a RAD7.

The device, as it stands, can provide a means for monitoring long-term changes in both radon and thoron sensitivity. After calibration at DURRIDGE Company, and with the optional Thoron Calibration Check Kit (sold separately), the device can be used for low-precision checking of both the RAD7’s radon sensitivity (monthly) and its thoron sensitivity (any time). A copy of the Durridge-issued Natural Rock Sample Calibration Form can be previewed here (PDF).

Natural Rock Sample Physical Specifications
Shipping Dimensions 16″ x 8″ x 8″ (41 cm x 20 cm x 20 cm)
Shipping Weight 5 pounds (2.3 kg)

$377.00Add to order

Natural Rock Sample Thoron Calibration

The Natural Rock Sample System comes already calibrated for radon. Thoron calibration is also offered as an option. Thoron calibration may be performed when the Natural Rock Sample System is purchased, or at any time thereafter.

$214.00Add to order

Thoron Calibration Check Kit

Check the thoron calibration of the RAD7 using the components in the Thoron Calibration Kit. The Thoron Calibration Check Kit consists of a Pump, Power Adaptors, Laboratory Drying Unit, Needle Valve, Custom Flow Meter, Tubing Set, and Carrying Case. (See photo and components diagram.) The Thoron Calibration Check Kit requires the Natural Rock Sample, which is not included.

$627.00Add to order

    DURRIDGE Natural Rock Sample
    DURRIDGE Natural Rock Sample

    Thoron Calibration Check Kit for Natural Rock Sample
    Thoron Calibration Check Kit for Natural Rock Sample (sold separately)

    Relay Box

    $219.00Add to order

    RAD7 accessory for issuing alerts and controlling the RAD7 operating environment

    At the end of each cycle the RAD7 can compare the measured radon concentration with each of two user-specified relay thresholds. If the radon level is higher than a particular amount, the RAD7 sets a relay. If it is lower, the relay is reset.

    Relays can be used to electronically trigger a warning mechanism at the lower threshold, and an alarm at the higher threshold. Relays can also be used to control ventilation equipment, or to change the concentration of radon in a sealed chamber, without the necessity of a computer.

    The DURRIDGE Relay Box facilitates this communication with external instruments.

    DURRIDGE Relay Box

    Relay Box

    Serial to Bluetooth Adaptor

    $133.00Add to order

    Adaptor for communicating wirelessly with the RAD7 from a computer

    DURRIDGE offers an optional Serial to Bluetooth adaptor to facilitate the transmission of radon data between the RAD7 and a Bluetooth-enabled Macintosh or Windows computer running DURRIDGE’s CAPTURE software. With the Bluetooth Adaptor, it becomes faster and more convenient to perform graphing and real-time data analysis. The adaptor has been tested across distances exceeding 40 meters, through walls and trees, and it is known to support 100 meter communication along uninterrupted lines of sight.

    The Serial to Bluetooth Adaptor may be powered by either an included AC adaptor or an optional 3.7V lithium ion battery, which is rated for 16 hours of continuous use. The included stub antenna may be replaced with an optional 2 dBi Dipole Antenna for an extended communication range.

    The Serial to Bluetooth Adaptor comes preconfigured for use with the RAD7. Printed documentation is included, explaining how to connect and reconfigure the adaptor.

    Serial to Bluetooth Adaptor Specifications
    Product ID Parani-SD1000
    Communications Protocol Bluetooth v2.0 + EDR
    Power 5~12VDC via standard AC adaptor or optional 3.7V 900 mAh battery with 16 hour capacity and 5 hour charge time.
    Dimensions 76 x 31 x 16 mm without battery pack
    76 x 31 x 31 mm with battery pack
    Weight 24 g without battery pack
    42 g with battery pack
    Warranty 3-year Limited Warranty
    Optional accessories
    Lithium Rechargeable 16 Hour Battery

    $54.00Add to order

    Extended Range 3 dBi Dipole Antenna

    $11.00Add to order

    DURRIDGE RAD7 with optional bluetooth adaptor

    Serial to Bluetooth Adaptor

    USB to Serial Adaptor Cable

    $52.00Add to order

    Adaptor cable for connecting the RAD7 to a Computer

    Durridge offers the StarTech USB to Serial Adaptor cable for connecting the RAD7 to your computer. This makes it possible to download, analyze, and export radon data using DURRIDGE’s CAPTURE software for Windows and macOS. It is also possible to issue RAD7 commands and control the RAD7 remotely.

    This adaptor cable is included with all newly purchased RAD7s, and it is also available separately.

    Adaptor Cable Specifications
    Hardware Chipset FTDI – FT232RL
    Serial Protocol RS232
    Connector Types 1 – DB-9 (9 Pin; D-Sub) Female
    1 – USB A (4 pin) Male
    OS Compatibility

    Windows XP/Vista/7/8/10
    Mac OS 10.X
    Cable Length 5 ft 11in (1.8m)
    Power Source USB Bus Powered
    Shipping Weight 0.5 lb (0.2 kg)
    Product Warranty 2 Years
    Included in Package

    USB to Serial Adaptor Cable
    Driver CD
    Instruction Manual
    • StarTech USB to Serial Adaptor Cable
      StarTech USB to Serial Adaptor Cable
    • StarTech USB to Serial Adaptor Pack
      StarTech USB to Serial Adaptor Pack
    Related Software


    Download Serial to USB Adaptor drivers

    Software Drivers (HTML)

    Water Switch

    $119.00Add to order

    Prevent water from entering the DRYSTIK and other sensitive devices

    The Water Switch is a device which cuts off power to a device should water enter the switch. It is specifically designed for the DRYSTIK. The Water Switch consists of a reed switch surrounded by a float that contains a magnet. If the float rises it will turn off the switch, cutting power to the DRYSTIK’s pump and preventing water from entering the device and saturing its sensitive NAFION tubing.

    DURRIDGE Water Switch Accessory

    Water Switch


    Water Switch Manual (PDF)