The RAD7 is able to measure both radon (222-Rn) and thoron (220-Rn) concentrations simultaneously and independently. The standard radon calibration is performed with a precision of better than 1% and we guarantee the RAD7 absolute accuracy for radon to be better than 5%. However thoron has a very short half life (about one minute) so that the concentration in the air will change during sample acquisition. For every minute the sample gas is in transit from the sampling point to the measurement chamber, the concentration of thoron in the sample will drop by half.

The RAD7 manual describes the standard setup for thoron sniffing. It is designed to minimize the transition time of the air sample from sampling point to measurement chamber. The pump runs continuously and the desiccant is in a small tube. In those conditions, the acquisition time is about one minute, so the default thoron sensitivity of the RAD7 is set at half the radon sensitivity. This setting is sufficient for most applications.

Occasionally a user requires more accurate thoron readings. For these applications DURRIDGE Company can provide, as an option, a specific thoron calibration for the setup used by the user. The detailed conditions of the calibration, including the air flow rate, may be chosen by the user and are clearly specified in the thoron calibration certificate issued by DURRIDGE. For any other setup, with a different flow rate or a different volume in the sample air path, that thoron calibration is no longer valid. For some projects, DURRIDGE Company has provided multiple thoron calibrations, each for a different setup of the RAD7 and air sample acquisition path.

Shipping Information

1. We recommend that you arrange for your RAD7 servicing ahead of time, to avoid possible delays. When sending your RAD7, please send the instrument only, without the cables and accessories, unless they are relevant to the work required. Pack the instrument upright in a box with one-inch padding all round. A 14″ cube box is suitable. Pack the box well, and seal it carefully.

2. International customers should be careful to prepare for the instrument’s shipment to the nearest calibration facility, and its subsequent return. There needs to be documentation proving that the instrument was previously imported into your country, otherwise you may be charged import duties for the return shipment. 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. You can declare and insure the instrument for USD $2,490. Please use the HS code 9801.00.1012. Please use the following description for RAD7: “RAD7 Electronic Radon Detector, not medical device.”

Foreign Shippers Declaration of US Goods Returned (PDF)

We suggest shipping via UPS or FEDEX. Please make sure the carrier will deliver the package to our door. We regret that we cannot be responsible for import duties, or for delivery charges incurred to our facilities either in the UK or USA.

3. We have had some problems with TNT, DHL and other special freight forwarding companies charging for clearing RAD7s through US customs. We have therefore been warning clients to avoid those two carriers and other special forwarding companies or be prepared to pay additional costs for shipping – possibly as much as $400 additional or more. So please be warned.

4. If you are in the European Union, or it is otherwise easier and more cost-effective, please return your RAD7 to our UK office. Otherwise, please ship to our USA office. The office addresses are as follows.

USA Office
DURRIDGE Company, Inc.
524 Boston Road
Billerica, MA 01821-2812, USA

Phone: (978) 667-9556
Fax: (978) 667-9557

UK Office
Sheffield Technology Park
Cooper Buildings
Arundel Street
Sheffield S1 2NS, UK

Phone: +44 (0)114 221 2003

5. CONTROLLED SHIPMENT method: We strongly suggest that you arrange for a “CONTROLLED SHIPMENT”. This means that your shipment will be delivered to us without incurring USA (and potentially UK) import customs and duty charges, and then it will be returned to you. It costs just a little more, but avoids import charges at both ends.

6. If you must ship to us some other way (via a freight forwarder, etc.), please specify that the shipment is sent “DDP”, which is the formal “INCOTERM” for “Delivered Duty Paid.” That means delivery to our door, with ALL charges paid. Unless you instruct us otherwise, we will return your RAD7 via the same shipping method you used to get 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.

It is important to make sure you prepare all the documentation you need to re-import the goods without being charged. Please write only in English on the commercial invoice. Please state on the invoice that the instrument is MADE IN USA and that it is being returned to the manufacturer for repair and recalibration. Also please mark the box with the serial number of the RAD7 as the RMA. You should also add our phone number as listed above, in case the customs office wants to call us.

Related Article

Technical Note: Thoron Calibration (HTML)