LAFARA is equipped with a double air handling unit (AHU) which operates follwing 3 stages:
- Air from outside passes through a first AHU to be conditioned. It results pre-filtered, cool and dry air;
- It then passes through 3 tanks filled with microporous charcoal (itself made from coconut shells) able to mechanically trap contaminating molecules such as gaseous radon (222Rn);
- Radon-free air then passes through a second AHU equipped with filters and which regulates the final temperature, pressure and hygrometry of the measurement room. A large part of the volume of treated air is recycled to minimise the amount of raw air to be treated.
The air in the measurement room is filtered comparably to a clean lab in order to obtain the best possible analysis conditions.
Radon is a radioactive gas derived from the natural radioactive suites from both uranium (219Rn & 222Rn) and thorium (220Rn, known as Thoron). It is naturally present – in small amounts – in the air as it is emitted by both ground and surrounding rocks. Its presence – and more importantly its variations – although low, can interfer with the gamma spectrometers and generate undesired signal together with those from the sample. We use a Rad-7 (Durridge) radon measurement device (alpha counter) to continuously monitor the radon level in the analysis room.