Active Moisture Exchanger [DRYSTIK]

Active Moisture Exchanger to reduce the humidity of the air entering the RAD7

The RAD7 radon monitor works 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 RAD7. As the air enters a drying unit (not included) on its way to the 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 diaphragm 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. Each is available with three different lengths of Nafion tubing, providing differing rates of humidity reduction. The premium 144-ADS-3 and 144-ADS-3R models are 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.

 

DRYSTIK Performance

DRYSTIK Model*	Initial Humidity	Humidity after 300 min.**
ADS-3-12	32%	17%
ADS-3-48	34%	10%
ADS-3-144	48%	7%

*Applies to both ruggedized and non-ruggedized DRYSTIK models.

**Humidity level achieved after 300 minutes at 22～28℃ with 100% internal pump duty cycle and no desiccant.