FLECs, also known as miniature emission cells, were
used for the first time in 1991 [22]. They are round,
stainless-steel saucers with a diameter of 150 mm and a
maximum height of 18 mm. The material from which
FLECs are made does not react with the target analytes
from building materials, and they have a silicone-rubber
seal to ensure that the system is airtight during analysis.
FLECs are very easy and cheap to operate.