This subcategory is extended from prerequisite 3 with the same objective that is to reduce ozone depletion. Two options are proposed then project team can select the most suitable options for implementation. The first option is zero use of refrigerants and the second option is using refrigerants and HVAC&R equipment which have minimum effect to atmosphere.
For the second options, the baseline value is calculated by given formula. It is the maximum allowance value which considers the impact to ozone depletion and global warming together. However, a weighted average will be calculated for multiple types of equipment. The HVAC units and equipment which contain less than 0.5 pounds (228 grams) of refrigerant are not taken into account for this subcategory. The significant prohibition is no use fire suppression system which contains ozone-depleting substances.