Scientists and environmentalists believe that ozone depleting substances (ODS) have caused so much damage to the ozone layer, which acts as a protective shield to the earth, as explained in the August newsletter. In response to the threat of ozone depletion, the United Nations Environment Program (UNEP) developed an international framework to control ozone depleting substances. This framework led to the Montreal Protocol on Ozone Depletion. The Montreal Protocol relates to the phase out of the production and consumption of ozone depleting substances. There is no specific requirement for equipment to be phased out. Equipment may be retained beyond the phase out dates as long as the refrigerant is safely contained. The Montreal has two sets of ODS phasing out dates, one for the developing countries and the other for the developed countries (more stringent).