Which statement about ODP values is true?

Which statement about ODP values is true?

• A. ODP values are absolute and do not depend on a reference substance.
• B. ODP values are relative to a reference substance, often CFC-11.
• C. ODP values apply only to hydrofluorocarbons.
• D. ODP equals GWP.

Answer: (B)

ODP values are a relative measure of how much a substance would deplete the stratospheric ozone, set by comparing it to a reference substance. The standard reference is CFC‑11, which is assigned an ODP of 1.0. This framing means other substances receive ODP values that reflect their potential to cause ozone depletion per unit mass, in relation to CFC‑11. Because it uses a baseline, ODP is not an absolute quantity and depends on the reference chosen and the chemistry of ozone destruction. Some substances have much lower ODP than CFC‑11, some have higher, and many modern refrigerants like HFCs have zero ODP because they don’t release ozone‑depleting halogens. It’s also important to distinguish ODP from GWP, which measures warming impact rather than ozone depletion.

ODP values are a relative measure of how much a substance would deplete the stratospheric ozone, set by comparing it to a reference substance. The standard reference is CFC‑11, which is assigned an ODP of 1.0. This framing means other substances receive ODP values that reflect their potential to cause ozone depletion per unit mass, in relation to CFC‑11. Because it uses a baseline, ODP is not an absolute quantity and depends on the reference chosen and the chemistry of ozone destruction. Some substances have much lower ODP than CFC‑11, some have higher, and many modern refrigerants like HFCs have zero ODP because they don’t release ozone‑depleting halogens. It’s also important to distinguish ODP from GWP, which measures warming impact rather than ozone depletion.