The RAD AQUA is an accessory for the DURRIDGE RAD7 radon detector that is used to bring the radon concentration in a closed air loop into equilibrium with the radon concentration in a flow-through water supply. The RAD AQUA consists of a spray chamber, called an “exchanger”, that brings the air and water into equilibrium. The radon in the air is monitored continuously by the RAD7.
The partition coefficient (the ratio of radon concentration in the water to that in the air at equilibrium) is determined by the temperature at the air/water interface. This temperature is measured with a temperature probe inserted into the exchanger. At typical room temperature the coefficient is about 0.25. That means the concentration of radon in the air is four times higher than in the water. As a result, the system’s sensitivity to radon in water is four times higher than the sensitivity to radon in air.
It takes time for the water to deliver radon to the air loop and for the RAD7 to respond to the changed radon concentration. With optimum configuration the response time of the system may be reduced to less than half an hour.