• SkillCat Team

ASHRAE Safety Classification

Updated: 7 days ago

EPA 608 Core Chapter 21 (Take full course for free)


In this module, we will discuss how the refrigerants are classified based on their flammability and toxicity. Skip to quiz!


1. Flammability and Toxicity Classes


ASHRAE is a global organization of engineers that establishes guidelines and standards in the HVAC industry. ASHRAE stands for American Society of Heating, Refrigeration, and Air Conditioning Engineers.


ASHRAE came up with a refrigerant safety classification system based on the flammability and toxicity of a refrigerant. This system is called Standard 34.This is the system that is used as a standard to understand the safety of different refrigerants.


Refrigerants are classified according to flammability and assigned to Class 1, 2, or 3.

  • Class 1 - Non-flammable refrigerants.

  • Class 2 - Low flammability refrigerants, and

  • Class 3 - High flammability refrigerants.

Refrigerants are also separated into two classes according to their toxicity.

  • Class A - Low-toxicity refrigerants

  • Class B - High-toxicity refrigerants


This table shows all the possible combinations of flammability classes and toxicity classes. We will go into more detail for this table after some quick comprehension questions.


2. 2L Subclass


ASHRAE recently added a new subclass (2L) for flammability. This would be between Class 2 for low flammability and Class 1 for non-flammables.


Class 2L refrigerants have low flammability and a slow burn rate. The slow burn rate is what distinguishes Class 2L from Class 2.


3. Best and Worst


A1 refrigerants are the safest to use. We can see from this chart that A1 refrigerants are non-flammable and have low toxicity. This makes sense, since Class A refers to low toxicity and Class 1 refers to non flammable refrigerants.


B3 refrigerants are the most dangerous to use. These refrigerants are highly flammable and have high toxicity. This makes sense, since Class B refers to high toxicity and Class 3 refers to high flammability.


4. Discussing Refrigerants


Examples of A3 refrigerants include:

  • R-290 (propane)

  • R-600a (isobutane)

  • R-441a (hydrocarbon blend)

Notice that these are all hydrocarbons. Hydrocarbons generally have low toxicity because they are more natural but are also highly flammable.


Since hydrocarbons are highly flammable, we need to take extra precaution with them. We will discuss specific procedures in the Safety module.


A2L refrigerants include HFO refrigerants like R-1234yf. HFO refrigerants generally fall in the category of A2L refrigerants because they contain fluorine. Fluorine makes HFO refrigerants less flammable than hydrocarbon refrigerants, which are highly flammable.



B2 refrigerants include:

  • R-717 (Ammonia)

Ammonia is a natural refrigerant, as we previously discussed. But it has high toxicity, so it’s not ideal for every type of application.


Examples of A1 refrigerants include:

  • R-11 (CFC)

  • R-22 (HCFC)

  • R-410a (HFC)

This is why R-11 and R-22 were popular as refrigerants in the past — they are A1 refrigerants, which are the safest to use.


R-410a is a blend of two HFC refrigerants that was developed to replace the use of R-22, an HCFC. We will discuss more about refrigerant blends in the next module.


R-410a is also classified as a A1 refrigerant, meaning it is among the safest to use. While it is non toxic and non-flammable, it can cause asphyxia. This is the most important safety issue when it comes to R-410a.


The ASHRAE classification system provides an general understanding of how safe a refrigerant is. It also helps us understand why a refrigerant might be dangerous to use. This allows us to think of precautions to take with specific refrigerants, based on the dangers present.

For example, with a class B refrigerant, we know to take precautions around its high toxicity. With a class 3 refrigerant, we know to take precautions around its high flammability.


We will discuss specific handling procedures in the General Safety module.



4. Conclusion


In this module, we discussed how the ASHRAE organization classified different refrigerants based on their flammability and toxicity.


Question #1: Which class refers to a refrigerant with high toxicity?

  1. 1

  2. 3

  3. A

  4. B

Scroll down for the answer...










Refrigerants are separated into two classes of toxicity. Class A is low toxicity, while Class B is high toxicity. So the correct answer is B for high toxicity.


Question #2: Which class refers to a refrigerant with low toxicity?

  1. 1

  2. 3

  3. A

  4. B

Scroll down for the answer...










Class B is high toxicity as we said for the previous question, so class A is low toxicity.


Question #3: Which class refers to a refrigerant that has low flammability?

  1. 1

  2. 2

  3. 3

  4. A

Scroll down for the answer...











The three classes for flammability are 1, 2, and 3. Class 2 is assigned to refrigerants with low flammability.


Question #4: Which class refers to a refrigerant that is not flammable at all?

  1. 1

  2. 2

  3. 3

  4. A

Scroll down for the answer...












Class 1 is assigned to non-flammable refrigerants.


Question #5: What does the new subclass (2L) describe?


  1. Alternate highly flammable refrigerants

  2. Refrigerants that are Class 2 and burn slowly

  3. Refrigerants that are Class 2 and take longer to be effective

  4. Refrigerants that are toxic

Scroll down for the answer...













The new subclass of refrigerants, called class 2L, are Class 2 refrigerants that burn slowly. Since they are still class 2, they still have low flammability.


Question #6: Which safety classification of refrigerants is most safe to use?


  1. B3

  2. B2L

  3. A3

  4. A1

Scroll down for the answer...













A1 refrigerants have low toxicity and low flammability, making them the safest to use. Recall that class A refrigerants have low toxicity and class 1 refrigerants are non-flammable.


Question #7: Which safety classification of refrigerants is most dangerous to use?


  1. B3

  2. B2L

  3. A3

  4. A1

Scroll down for the answer...














B3 refrigerants have high toxicity and high flammability, making them the most dangerous to use. Recall that class B refrigerants have high toxicity and class 3 refrigerants are highly flammable.


Question #8: B2 refrigerants are more dangerous than which of the following? (Select all that apply)

  1. B1

  2. B3

  3. A1

  4. A2

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B2 refrigerants have high toxicity (Class B) and flammability (Class 2). Since they are highly toxic, they are more dangerous than c)A1 and d)A2 refrigerants. Since they have low flammability, they are more dangerous than B1 refrigerants, which are not flammable (Class 1).


Question #9: B2 refrigerants are safer than which of the following?


  1. B1

  2. B3

  3. A1

  4. A2

Scroll down for the answer...




















B2 refrigerants are safer than B3 refrigerants. B3 refrigerants are highly flammable, while B2 refrigerants only have low flammability.


Question #10: Hydrocarbons: (Select all that apply)

  1. Are generally A3 refrigerants

  2. Have high toxicity

  3. Have low flammability

  4. Are safe to use because they are natural refrigerants

Scroll down for the answer...




















Hydrocarbons are A3 refrigerants. This means they have low toxicity but are highly flammable. While they are non-ozone depleting, they must be handled with care due to their flammability.


Question #11: Ammonia is safe to use because it is a natural refrigerant.

  1. True

  2. False

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This is false. Ammonia (R-717) is a B2 refrigerant. This means it is toxic, so it is not completely safe to use just because it is a natural refrigerant.


Question #12: HFO refrigerants are this safety classification:

  1. A2L

  2. A2

  3. B2

  4. B2L

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HFO refrigerants are generally classified as A2L refrigerants.


Question #13: R-410a is a A1 refrigerant. It is non-toxic and has low flammability, making it one of the safest refrigerants to use.

  1. True

  2. False

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True. A1 refrigerants are the safest to use and R-410a is an A1 refrigerant.


Question #14: What are the main safety concerns with R-410a?

  1. None, it’s an A1 refrigerant so there are no safety concerns

  2. Toxicity

  3. Blood oxygenation

  4. Asphyxia

Scroll down for the answer...











Even though R-410a is non toxic and has low flammability, it can still cause asphyxia. This is the main concern when it comes to handling R-410a.















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