• SkillCat Team

Ozone Depletion Potential

Updated: 2 days ago

EPA 608 Core Chapter 19 (Take full course for free)


In this module, we will define ozone depletion potential and how it is used to determine the harmfulness of different refrigerants. Skip to quiz!


1. Ozone Depletion


Recall from our Ozone module that ozone is a molecule found in our atmosphere. It absorbs and reflects harmful UV rays from the sun.


When released into the atmosphere, certain refrigerants are especially potent at destroying ozone. This is because the refrigerants contain chlorine.

CFCs and HCFCs are the most harmful because they contain chlorine. These refrigerants are also relatively stable, meaning they don’t get destroyed easily by rain or sunlight. This makes it more likely that they will reach the stratosphere, where the ozone layer is.


Refrigerant chemicals have a lifespan of 70-100 years — this is how long they will stay in the atmosphere, destroying ozone until they are broken down naturally.


2. ODP Number


We can characterize the potential of a refrigerant to destroy ozone as its Ozone Depletion Potential (ODP). The ODP number we assign to a refrigerant tells us how harmful that refrigerant is to ozone in the atmosphere.

CFCs are the most destructive to the ozone layer so its ODP is the highest. The next most destructive are HCFCs.


You can think of ODP as similar to the Richter scale, which describes the severity of earthquakes. On the Richter scale, the higher the number is, the larger the magnitude of the earthquake.


In terms of ODP, the higher that number is, the more harmful the refrigerant is for the ozone layer.


3. Highest ODP


ODP is a scale that determines how much ozone depleting potential substances have compared to each other.


Of all modern refrigerants, starting with CFCs, the highest ODP is 1. R-11 and R-12, which are both CFCs, both have an ODP of 1. All the HCFC, HFC, and newer refrigerants have an ODP of less than 1. This is because they are less harmful to the ozone layer than R-11 and R-12.


Note that there are older refrigerants that have an ODP of greater than 1. This means that they are more harmful to the ozone layer than R-11 and R-12. This includes halons, which were also used in fire extinguishers. These have long been banned.


4. ODP Comparison


Let’s look at the ODPs of several commonly used pure refrigerants. This chart shows the ozone depleting potentials of different examples of each type of refrigerants.


Notice that R-11 has the highest ODP of 1. R-11 is the most destructive refrigerant and we compare all other refrigerants against it. Note also that R-11 is a CFC, which we have already discussed is the most destructive refrigerant to ozone.

R-22, which is an HCFC, has an ozone depletion potential of 0.05. This means it still depletes the ozone layer but it is much less ozone depleting than CFC.


R-410a, which is an HFC refrigerant, has an ozone depletion potential of 0. R-1234yf, which is an HFO refrigerant, also has an ozone depletion potential of 0. As we discussed, this is because HFCs and HFOs do not contain chlorine so they do not deplete ozone.


Natural refrigerants, like nitrogen, carbon dioxide, and water, also have an ODP of 0 since they do not contain chlorine. Other natural refrigerants include hydrocarbons (HCs) such as propane (R-290) and isobutane (R-600a).


5. Conclusion


In this module, we defined ozone depletion potential. We also compared the ozone depletion potential of different refrigerants.


Question #1: The lowest number for an ozone depletion potential (ODP) is 1.

  1. True

  2. False

Scroll down for the answer...











False! The highest ODP is 1 for R-11, a CFC refrigerant. The potential of any refrigerant to deplete the ozone layer is compared to the ODP of R-11 and will be lower.


Question #2: Which type of refrigerants are most harmful to the ozone layer?

  1. HFOs

  2. UFOs

  3. HCFCs

  4. CFCs

Scroll down for the answer...











CFCs have the highest ozone depletion potential of all the types of refrigerants because of the three chlorine atoms it contained.


Question #3: Which types of refrigerants are least harmful to the ozone layer? (Select all that apply)

  1. CFCs

  2. HCFCs

  3. HFCs

  4. HFOs

Scroll down for the answer...











HFCs and HFOs are non ozone depleting since they do not have chlorine atoms. They both have an ODP of 0.


But CFCs and HCFCs, contain chlorine atoms. So they are the most ozone depleting.


Question #4: What is highest possible ODP for any CFC, HCFC, HFC, or HFO refrigerant?

  1. 0

  2. 1

  3. 100

  4. Infinite

Scroll down for the answer...











The highest possible ODP for these refrigerants is 1 for R-11, a CFC refrigerant. The potential of any refrigerant to deplete the ozone layer is compared to the ODP of R-11 and will be lower.


Question #5: What is the least possible ODP for a refrigerant?

  1. 0

  2. 1

  3. 100

  4. None

Scroll down for the answer...











The highest ODP is 1 for R-11, a CFC. If a refrigerant does not contain chlorine and does not destroy ozone, it has an ozone depletion potential (ODP) of 0.


Question #6: What is the ODP of R-600a?

  1. 1

  2. 0

  3. 0.5

  4. 0.25

Scroll down for the answer...











R-600a is isobutane, which is a natural refrigerant.


Since natural refrigerants do not contain chlorine, they do not deplete the ozone layer. So their ODP is 0.


Question #7: Which of the following refrigerants have an ODP of greater than 0?

  1. R-12

  2. R-22

  3. R-410a

  4. R-600a

Scroll down for the answer...











R-12 has an ODP of 1. It is a CFC refrigerant. R-22 has an ODP of 0.5. It is an HCFC refrigerant.


Question #8: What is the ODP of R-441a?

  1. 0

  2. 0.1

  3. 0.2

  4. 1

Scroll down for the answer...











R-441a is a hydrocarbon refrigerant. Hydrocarbons are natural refrigerants and do not contain chlorine, they do not deplete the ozone layer. So all hydrocarbons have an ODP of 0.


Question #9: If a refrigerant has an ODP of 0.5, which of the following are true? (Select all that apply)

  1. It contains chlorine

  2. It might contain chlorine

  3. It could be R-22

  4. It could be R-1234yf

Scroll down for the answer...











If a refrigerant has an ODP of anything greater than 0, it must contain chlorine, since it is chlorine that is responsible for destroying ozone. Examples of this include R-11, which has an ODP of 1 and R-22, which has an ODP of 0.5. They both contain chlorine.



16 views0 comments

Recent Posts

See All

© LearnToDrill 2020

  • Grey YouTube Icon