Ozone depleting substances
Hydrogen (H2) and hydrocarbons (CxHy) absorb ultra-violet (UV) light. They protect a planets surface from excessive UV radiation. These gases are removed by Oxygen (O2) when a planet is terraformed. The planets surface is then exposed to UV radiation until a layer of ozone (O3) forms in the upper atmosphere. The ozone layer then provides a protective barrier against UV radiation. Fluorine (F), Chlorine (Cl) and Bromine (Br) act as catalysts to breakdown ozone. They're not usually found in the upper atmosphere, but can be carried there by halohydrocarbons. Most halohydrocarbons are also super greenhouse gases. As such, halohydrocarbons should not be used when terraforming a planet. The Montreal Protocol expressly forbits the creation and/or use of many halohydrocarbons. The following is a list of halohydrocarbons know to deplete ozone:
| Class I | ||
| CFC-11 | CCl3F | Trichlorofluoromethane |
| CFC-12 | CCl2F2 | Dichlorodifluoromethane |
| CFC-13 | CClF3 | Chlorotrifluoromethane |
| CFC-111 | C2Cl5F | Pentachlorofluoroethane |
| CFC-112 | C2Cl4F2 | Tetrachlorodifluoroethane |
| CFC-113 | C2Cl3F3 | Trichlorotrifluoroethane |
| CFC-114 | C2Cl2F4 | Dichlorotetrafluoroethane |
| CFC-115 | C2C2F5 | Chloropentafluoroethane |
| CFC-211 | C3Cl7F3 | Heptachlorofluoropropane |
| CFC-212 | C3Cl6F2 | Hexachlorodifluoropropane |
| CFC-213 | C3Cl5F3 | Pentachlorotrifluoropropane |
| CFC-214 | C3Cl4F4 | Tetrachlorotetrafluoropropane |
| CFC-215 | C3Cl3F5 | Trichloropentafluoropropane |
| CFC-216 | C3Cl2F6 | Dichlorohexafluoropropane |
| CFC-217 | C3ClF7 | Chloroheptafluoropropane |
| Halon 1011 | CH2BrCl | Bromochloromethane |
| Halon 1202 | CBr2F2 | Dibromodifluoromethane |
| Halon 1211 | CF2ClBr | Bromochlorofluoromethane |
| Halon 1301 | CF3Br | Bromotrifluoromethane |
| Halon 2402 | C2F4Br2 | Dibromotetrafluoroethane |
| Chloroform | CCl4 | Tetrachloromethane |
| Methyl Chloroform | CHCl3 | 1,1,1-Trichloroethane |
| Methyl Bromide | CH3Br | Bromomethane |
| Class II | ||
| HCFC-21 | CHFCl2 | |
| HCFC-22 | CHF2Cl | |
| HCFC-31 | CH2FCl | |
| HCFC-121 | C2HFCl4 | |
| HCFC-122 | C2HFCl3 | |
| HCFC-123a | C2HF3Cl2 | |
| HCFC-123b | CHCl2CF3 | |
| HCFC-124a | C2HF4Cl | |
| HCFC-124b | CHFCLCF3 | |
| HCFC-131 | C2H2FCl2 | |
| HCFC-132 | C2H2F2Cl2 | |
| HCFC-133 | C2H2F3HCl | |
| HCFC-141a | C2H3FCl2 | |
| HCFC-141b | CH3CFCL2 | |
| HCFC-142a | C2H3F2Cl | |
| HCFC-142b | CH3CF2Cl | |
| HCFC-151 | C2H4FCl | |
| HCFC-221 | C3HFCL6 | |
| HCFC-222 | C3HF2CL5 | |
| HCFC-223 | C3HF3Cl4 | |
| HCFC-224 | C3HF4Cl3 | |
| HCFC-225 | C3HF5Cl2 | |
| HCFC-225ca | CF3CF2CHCL2 | |
| HCFC-225cb | CF2ClCF2CHClF | |
| HCFC-226 | C3HF6Cl | |
| HCFC-231 | C3H2Cl5 | |
| HCFC-232 | C3H2F2Cl4 | |
| HCFC-233 | C3H2F3Cl3 | |
| HCFC-234 | C3H2F4Cl2 | |
| HCFC-235 | C3H2F5Cl | |
| HCFC-241 | C3H3F2Cl3 | |
| HCFC-242 | C3H3F2Cl3 | |
| HCFC-243 | C3H3F3Cl2 | |
| HCFC-244 | C3H3F4Cl | |
| HCFC-251 | C3H4FCl3 | |
| HCFC-252 | C3H4F2Cl2 | |
| HCFC-253 | C3H4F3Cl | |
| HCFC-261 | C3H5FCl2 | |
| HCFC-262 | C3H5F2Cl | |
| HCFC-271 | C3H6FCl |