Using Model 1027 continuous radon monitor

a test of reducing radon level by ventilation in underground space was done. Four different types of ventilation

i.e. by air pump (P)

by air intake blower (B)

by air pump and air intake blower simultaneously (PBS)

and by air pump and air intake blower in turn (PBT)

were examined. We found that efficiency of PBS is the highest among these ventilation types. Having ventilated the underground space with PBS for 1

2 or 3 hours in three different days

and having observed the radon concentration change in the following 24 hours

we can conclude that it is safe for people to stay there during the eight working hours if the underground space is ventilated for 2 hours everyday in the morning.