One of these free atoms of oxygen should then be attached to the molecular oxygen to make an ozone molecule. The free atom can then bond with another oxygen atom to form a molecule of oxygen or it could strike an ozone molecule, break it up, and form two oxygen molecules. If a free oxygen atom hits the chlorine monoxide, the chlorine can be liberated and an oxygen molecule will be formed. The chlorine atom is then able to strike another ozone molecule. Many of the chemicals used in place of CFC propellants are safe for the environment.
Environmental agencies require extensive testing before a chemical can be used as a propellant.
If a chemical that was deemed safe should later prove to be harmful, government regulations require that use of the chemical must cease. Look at the image of the hole in the ozone layer. Measurements taken in some summer months have shown ozone levels over the southern ice cap to be well in excess of 300 DU, a full 100 DU more than the levels recorded in 1996, when the hole reached record size. Volcanoes do produce chemicals which break down ozone. However, volcanic eruptions do not have the power to send these chemicals into the upper atmosphere, and the sheer mass of many of these chemicals causes them to fall quickly from air currents to the Earth.