The RAD8 and RAD7 radon monitors work most effectively when the incoming air sample has a low relative humidity. The DURRIDGE DRYSTIK Model ADS-3 transfers moisture from the incoming air to the air being pumped out of the RAD8 or RAD7. As the air enters a drying unit (not included) on its way to the RAD8 or RAD7, it will have already lost most of its moisture, greatly extending the life of the desiccant in the drying unit. In certain cases the need for desiccant is eliminated altogether.

The DRYSTIK has at its heart a Nafion humidity exchanger with brushless pump, fixed and variable flow limiters, and a programmable Duty Cycle Controller. These are all contained in a compact enclosure. The DRYSTIK’s pump compresses the sample air inside the membrane tubing, initiating the transfer of water molecules to the outer purge flow, drying the incoming air as it moves through the device.

The DRYSTIK is available in two enclosures: a standard case which is suitable for laboratory use, and a ruggedized Pelican case which is ideal for demanding field work. The instrument is capable of bringing the relative humidity of air flowing at 0.15 L/min down below 10% in less than four hours when operating with a 40% duty cycle, and the humidity can be maintained below 6% indefinitely without any desiccant. This allows a RAD7 to operate under optimum conditions with the highest sensitivity and lowest operating cost. At a higher flow rate of 1.2 L/min, the DRYSTIK can bring the RH down below 12%, which is sufficient for enhanced-sensitivity thoron measurement.

For soil gas measurement, the DRYSTIK provides high flow capability for thoron detection. For radon, the ability to lower the flow with the built-in Duty Cycle Controller means that continuous soil gas readings may be made indefinitely, without any risk of fresh air diluting the soil gas sample by diffusing down to the extraction point.

Principle of Operation

The DRYSTIK operates on a principle involving two tubes, one inside the other. The inner tube is made of NAFION, a Teflon based material that permits the movement of water molecules, while blocking air and radon. The air sample flows along the inner tube on its way to a drying unit, while the space around the inner tube is purged with dry air coming from the outlet of the RAD8 or RAD7.

Summary of Benefits

The DRYSTIK enables users to enjoy the full capabilities provided by the superior RAD8 and RAD7 technology, with its rapid response and recovery, vanishingly small background, thoron specific sniffing, and radon-in-water accessories, with the need to replace and/or regenerate the desiccant only after a long period. The cost of replacing used desiccant becomes insignificant.

With a pump upstream and a needle valve downstream of the NAFION tube, compressing the air inside the tube, the DRYSTIK works regeneratively, and can even eliminate the need for desiccant altogether.

Replacement Pumps for DRYSTIK

The DRYSTIK contains a premium quality pump, mounted on a shock- and sound-absorbing bridge plate. The pump has an expected life span of 10,000 hours of constant use (or 50,000 hours assuming a typical 20% pump duty cycle). Older DRYSTIKs from 2013 and earlier contain less robust pumps, and they may be shipped back to DURRIDGE to be upgraded if desired. Please contact us for details.

Related Products