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DURRIDGE provides several RAD7 services including calibration, repair, and software upgrades. These services, plus our shipping and receiving policies, are explained in detail below.



RAD7 Calibration

The EPA recommends, and we agree, that continuous radon monitors be calibrated at least every year. RAD7 calibration requires four to five working days from the receipt of the instrument. As a preliminary to recalibration, we inspect and test every RAD7. If additional service is required, this may delay the return of the instrument.

DURRIDGE maintains a radon calibration facility that includes a controlled, standard source of radon gas. All RAD7 alignment and calibration is conducted at the DURRIDGE offices, as well as basic testing and quality assurance. We determine calibration factors by direct comparison to "master" RAD7s, which were themselves compared with EPA and DOE instruments, and which have participated in international inter-comparisons of radon instrumentation. The calibration accuracy is independently verified by direct determination of the radon chamber level from the calibrated activity and emission of the standard radon source. In addition, we regularly inter-compare with other radon chambers. We achieve a reproducibility of better than 2% with our standard RAD7 calibration. Overall calibration accuracy is better than ±5%.


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


Thoron Calibration

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.


RAD7 Repair

If you discover that your RAD7 is malfunctioning, we recommend that you first call DURRIDGE and talk to a technician. A surprising number of minor "disasters" can be avoided by long-distance consultation.The next step, if consultation fails, is usually to send your instrument in for evaluation and repair. Please send any documentation of the problem that you might have (notes, printouts, etc.) and a short note describing the problem. Be sure that you put your name and telephone number on the note. Within 48 hours of our receipt of the instrument, we will call you to give a diagnosis.

Bear in mind that a repaired instrument often requires complete re-calibration, so a one-week turn-around may be the best we can do. If you absolutely need an instrument during the repair time we can sometimes arrange to send you a "loaner" instrument.


Firmware Upgrades

Whenever you send your RAD7 in for repair or calibration, you have the option of having the latest available software installed. Most RAD7's can be upgraded to the latest hardware configuration as well. You will be informed periodically of whatever new features are available for your RAD7. Please advise if you want to have an upgrade made. We intend to keep our RAD7 customers happy by keeping their instruments up-to-date and state-of-the-art.


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 accessories, unless they are relevant to the problem.

    Each RAD7 is originally shipped in a plastic bag, packed in a box with "popcorn", and finally packed inside another box that also holds all the accessories. The inner box by itself is too small for the return trip, when you need a calibration or repair job. You will need to find a bigger box, with space for one inch packing all round the RAD7. A 14" cube box is fine. Pack the box well, with at least an inch of padding all around, and seal it carefully.

  2. Inbound shipments to DURRIDGE must be prepaid 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. If you are in the European Union, or it is otherwise easier and more cost-effective for you to 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

  4. CONTROLLED SHIPMENT method: We strongly suggest that you contact one of the major couriers (UPS, FedEX, DHL, TNT, etc.) and arrange 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.

  5. If you must ship to us some other way (via a freight forwarder, etc.), please specify that the shipment is sent "DDS", 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 - from "slow boat" to "next day air" - freight collect.  DURRIDGE can pay for the return shipment CIF (Cost, Insurance, & Freight) to you, but our cost will be invoiced to you before shipment.
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