Answer:

ozone

Answer	Crossword Clue
OZONE	Fresh air, informally
OZONE	UV-absorbing layer
OZONE	Allotropic form of oxygen

OZONE	Odorous oxygen
OZONE	There's a "hole" in it
OZONE	Thunderstorm by-product
OZONE	Sun screen
OZONE	Kind of layer
OZONE	Blue gas in the greenhouse effect
OZONE	Shrinking layer
OZONE	Form of oxygen

OZONE	Endangered layer
OZONE	Global warming factor
OZONE	Holey layer?
OZONE	Space cadet's place?
OZONE	Ultraviolet blocker
OZONE	Atmosphere layer
OZONE	Air way up there
OZONE	Ultraviolet filter

OZONE	Molecule formed by lightning
OZONE	Ultraviolet ray absorber
OZONE	Damaged layer
OZONE	Important layer
OZONE	Controversial stratum
OZONE	Oxygen allotrope
OZONE	Imperiled layer
OZONE	Layer that absorbs ultraviolet rays

OZONE	Layer to be concerned about
OZONE	Electrical storm byproduct
OZONE	Protective layer
OZONE	.. hole
OZONE	Atmospheric layer
OZONE	Gas that both protects and pollutes
OZONE	Greenhouse gas
OZONE	Hole site

OZONE	O3
OZONE	Triatomic pollutant
OZONE	UV ray absorber
OZONE	Depleted layer
OZONE	Layer to worry about