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any other setup, with a different flow rate or a different volume in the sample air path, that thoron calibration is no longer valid.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.

Shipping Information

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 accessorie, unless they are relevant to the problem.

Each RAD7 is originally shipped to 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.

All return shipments to DURRIDGE must be prepaid, and unless you instruct us otherwise, we'll return it to you via the same shipping method you used to get it to us - from "slow boat" to "next day air" - freight collect.