DURRIDGE’s RAD7 Calibration Service includes a comprehensive range of tests, routine maintenance, and adjustment of any parameters necessary to bring your RAD7 up to full specifications, as well as replacement, if needed, of consumable components such as the battery, pump, and NVRAM chip, and up to a half hour of labor for any additional minor repairs.

The cost of the RAD7 Calibration Service is US $550 / GBP £420 / EUR €475.

DURRIDGE’s radon calibration facilities in the USA and the UK have their own controlled, standard source of radon gas. All RAD7 testing, calibration, and quality assurance is performed at DURRIDGE by DURRIDGE-qualified staff.

The DURRIDGE calibration system is compared, to a precision of better than 1%, with a secondary standard chamber, which is in turn calibrated by comparison with a NIST radon standard supplied through the U.S. EPA. The DURRIDGE system accuracy is also independently checked by making a direct determination of the system radon level from the activity and emission of our European standard radon source. Our Calibration Service achieves a reproducibility of better than ±2% and an overall calibration accuracy of better than ±5%. (Ever vigilant, we also compare our instruments with other radon measurement devices through periodic participation in inter-comparison workshops held worldwide.)

The U.S. EPA recommends that continuous radon monitors, such as the RAD7, be calibrated at least once per year, and DURRIDGE agrees.

Shipping Information

1. You can send us your RAD7 at any time to either one of our Calibration facilities (USA and UK), listed below (see important, specific instructions for each below).

2. We need the RAD7 in house for 10 days, so the total time a RAD7 will be away from your facility will be 10 days plus the time the RAD7 spends in transit. If additional service or repair is required, this may delay the return of the instrument.

3. When sending your RAD7, please send the instrument only, without the cables and accessories. Pack the instrument upright in a box with one-inch (2.2cm) padding all around. A 14x14x14in (or 36x36x36cm) box is suitable. Pack the box well, and seal it carefully. Please include your contact info with the package.

4. International customers must be very careful, to avoid substantial extra shipping charges and delays, both for shipping to the nearest calibration facility, and for its subsequent return.

5. Commercial Invoice check-list:

  • For your courier or freight forwarder, you will need to provide a Commercial Invoice.
  • Please write only in English on the commercial invoice.
  • Please use the following description for the RAD7: “RAD7 Electronic Radon Detector, returned to manufacturer for service”. Please also include this description on the air waybill (AWB).
  • Insured value US$2,490.
  • Please state on the invoice that the instrument is MADE IN USA and that it is being “returned to the manufacturer temporarily for repair and recalibration“.
  • Please use the HS (Commodity) code 9030.10.00.
  • Please mark the box with the serial number of the RAD7 (as the RMA – Return Merchandise Authorization).
  • Please add the phone number of the Calibration facility you choose, in case the Customs Office wants to call us.
  • Next, you must ensure that your courier (i.e. UPS, FedEX) or freight forwarder will deliver the package to our door. The formal “INCOTERM” for this is “DDP”, which means “Delivered Duty Paid.”
  • We will not pay or be responsible for USA or UK import duties, or Customs clearance charges. Your shipper must be told this when you arrange your shipment.
  • It is important to make sure you prepare all the documentation you need to reimport the goods back into your country without being charged.
  • For the Return to you: unless you instruct us otherwise, we will return your RAD7 via the same shipping method you used to deliver it to us, Freight Collect. DURRIDGE can pay for the return shipment CPT (“Carriage Paid To”) to you, but our cost will be invoiced to you before shipment.

If we can help further, please email us at

Specific info for SHIPPING TO OUR USA FACILITY (from outside the USA)

DURRIDGE Company, Inc.
524 Boston Road
Billerica, MA 01821-2812, USA
Phone: +1 (978) 667-9556
Fax: +1 (978) 667-9557

Declaration Form

  • There needs to be documentation proving that the instrument was previously imported into your country, otherwise you may be charged import duties when the instrument is returned to your country.
  • Please fill out the declaration form provided below. Attach the completed declaration form to the commercial invoice. If the invoice is scanned and submitted electronically, please scan the declaration form and submit it electronically as well.

Foreign Shippers Declaration of US Goods Returned (PDF)

Specific info for SHIPPING TO OUR UK FACILITY

DURRIDGE UK Ltd.
Sheffield Technology Park
Cooper Buildings
Arundel Street
Sheffield S1 2NS, UK
Phone: +44 (0)114 221 2003

For Customers inside the EU:
No special paperwork is required for shipping within the EU Customs Union.

For Customers Outside the EU:
Our UK office has a special authorisation from the UK tax authority (HMRC) to “import RAD7s temporarily for calibration and repair“, without them being assessed for UK import duty. So when sending your RAD7 to our UK office, please state on the commercial invoice that the instrument is being imported using our Inward Processing Authorisation reference IP/0920/142/18. Failure to do so may result in import duty being charged, for which you will be responsible.

DURRIDGE calibration chamber


DURRIDGE calibration tool

DURRIDGE’s calibration system continuously monitors RAD7 performance in a controlled environment over a multi-day period.


DURRIDGE calibration technician

DURRIDGE calibration technician