Before a worker enters the space, the air must be tested to make sure there is enough oxygen to breathe and there are no chemical hazards.
(a worker; enters; the space) (the air; must be tested; to make sure there is enough oxygen to breathe and there are no chemical hazards; T:Before a worker enters the space)
a worker the air
enters must be tested
the space
to make sure there is enough oxygen to breathe and there are no chemical hazards T:Before a worker enters the space