R438A RefrigerantMO99 / KDD5 · A1 R22 retrofit blend · broad legacy equipment relevance
R438A, widely known as ISCEON MO99 or KDD5, is a nonflammable retrofit refrigerant developed mainly for existing R22 equipment. It was designed to provide a relatively easy R22 transition path while keeping A1 safety, which is why it became one of the most recognized retrofit blends in legacy HVAC and refrigeration service work. Today, its practical relevance remains high in the installed base, even though its GWP is far above modern low-GWP targets.
What is R438A refrigerant?
R438A is important because it is a real field refrigerant, not just a catalog number. EPA composition tables identify the blend as 8.5% R32, 45% R125, 44.2% R134a, 1.7% R600 and 0.6% R601a. EPA SNAP tables commonly show ODP 0, GWP 2,270 and A1 classification, with acceptability in multiple legacy air-conditioning and refrigeration end uses. That makes R438A a strong knowledge topic wherever readers still manage large populations of R22 equipment.
R438A, widely known as ISCEON MO99 or KDD5, is a nonflammable retrofit refrigerant developed mainly for existing R22 equipment. It was designed to provide a relatively easy R22 transition path while keeping A1 safety, which is why it became one of the most recognized retrofit blends in legacy HVAC and refrigeration service work. Today, its practical relevance remains high in the installed base, even though its GWP is far above modern low-GWP targets.
R438A technical properties
Core reference data and selection notes for R438A based on the positioning used in this page.
| Designation | R438A | ASHRAE designation; MO99 / KDD5 |
|---|---|---|
| Nominal composition | R32 / R125 / R134a / R600 / R601a = 8.5 / 45 / 44.2 / 1.7 / 0.6 | EPA composition table |
| Refrigerant type | Zeotropic blend | Multi-component retrofit blend |
| ODP | 0 | No ozone depletion |
| 100-year GWP | 2,270 | EPA SNAP tables |
| Safety classification | A1 | Nonflammable |
| Primary role | R22 retrofit refrigerant | Air conditioning and refrigeration |
| Trade names | ISCEON MO99, KDD5 | Widely recognized names |
| Service positioning | Legacy system retrofit | Installed-base management |
| Selection theme | Ease of R22 transition with A1 safety | Field-service relevance |
Where R438A is used
These are the most relevant application contexts for R438A in practical HVACR and thermal-system discussions.
Residential and light-commercial AC / heat pumps
EPA SNAP tables list R438A as acceptable in these legacy categories.
Industrial process air conditioning
EPA also lists R438A in industrial process air conditioning.
Commercial refrigeration
R438A appears in multiple legacy refrigeration service discussions.
Household and stand-alone equipment legacy contexts
It has been listed in several historical SNAP end-use tables, though not all new high-GWP uses remain favored.
Installed R22 base management
Useful where owners need continued support or staged transition of older systems.
Service retrofits
Often considered when full equipment replacement is not yet practical.
Detailed analysis
Why R438A became one of the best-known R22 retrofit blends
R438A earned real market attention because it targeted a massive installed base of R22 equipment. Owners wanted something easier than full replacement, and contractors often preferred an A1 refrigerant that fit familiar service practice more comfortably than flammable alternatives.
This gave R438A lasting relevance in retrofit conversations and field-service education.
As a result, an R438A page should speak to real installed-base decision making, not just list composition percentages.
R438A is practical, but it is not a low-GWP future solution
With a GWP of 2,270, R438A is much cleaner from an ozone perspective than R22 because it has zero ODP. But from a climate perspective, it is still a relatively high-GWP refrigerant.
That means its value is mostly practical and transitional: helping support or extend legacy systems, not defining the final destination of refrigerant transition strategy.
Content that explains this dual reality is much more credible than simple sales language.
Why the tiny hydrocarbon fractions matter
R438A includes small amounts of R600 and R601a in addition to the main HFC components. These small fractions help tune overall system behavior and retrofit performance.
However, the finished blend remains classified A1. That is why the page should always focus on the finished refrigerant classification rather than overinterpreting individual component flammability.
This also shows why a blend-specific detector and proper refrigerant identification matter.
When R438A content is still valuable for SEO and GEO
Even though the industry is moving toward lower-GWP options, search demand around R22 retrofits remains relevant because installed equipment persists for many years.
Readers often search R438A when they are making a real service or asset-management decision, which makes it a strong intent-driven topic.
That is exactly the kind of evergreen-but-practical content cluster a refrigerant site should keep building.
R438A vs R427A
A focused side-by-side comparison to help readers understand selection differences.
| Comparison Point | R438A | R427A |
|---|---|---|
| Primary role | R22 retrofit | R22 retrofit |
| Safety class | A1 | A1 |
| ODP | 0 | 0 |
| 100-year GWP | 2,270 | 2,140 |
| Type | Zeotropic HFC/HC blend | Zeotropic HFC blend |
| Special note | Contains small hydrocarbon fractions | No hydrocarbon fraction |
| Field positioning | Very common retrofit reference | Easy retrofit positioning |
R438A safety: A1 helps, but blend handling and retrofit validation are still essential
R438A is A1, which is one reason it became popular in retrofit work. However, it is still a pressure refrigerant blend, and retrofit suitability should be verified in the actual system. Correct charging, oil assessment, control behavior and performance checks remain part of good practice.
- A1 classification: No lower-flammability label.
- Blend service practice: Use correct PT chart and charge as a blend.
- Retrofit review: Check the real equipment rather than assuming universal compatibility.
Leak detection
Leak detection should be validated for halogenated refrigerants and, where relevant, the finished R438A blend behavior. Portable service detectors and fixed monitoring systems solve different problems and should not be treated as interchangeable. GasNose provides a helpful broader reference point for refrigerant detection planning.
U.S. regulations
EPA SNAP tables list R438A with ODP 0, GWP 2,270 and A1 safety, and they show acceptability in multiple legacy air-conditioning and refrigeration categories. At the same time, newer U.S. transition policy trends make very high-GWP HFC blends less attractive for new long-term strategies.
EU / international context
In Europe, R438A is similarly best understood as an installed-base or retrofit refrigerant, not as a leading low-GWP choice for new projects.
Phaseout / long-term view
R438A is not an ozone-depleting refrigerant, but its relatively high GWP limits its long-term strategic appeal. It remains most relevant where legacy R22 equipment still needs support.
Misconceptions to avoid
Several refrigerants are misunderstood because readers focus on one number or one trade name. These points help keep the topic accurate.
“R438A is a low-GWP refrigerant because it replaces R22.”
It has zero ODP and practical retrofit value, but a GWP of 2,270 is still high.
“R438A is just R22 with a new label.”
It is a distinct five-component blend with different properties and service behavior.
“A1 means any R22 system can use it without checks.”
Retrofit suitability still depends on the actual equipment and service condition.
“The hydrocarbon components make the finished blend flammable.”
The finished refrigerant is still classified A1.
R438A refrigerant FAQ
Concise answers to common questions about properties, uses, safety class and regulatory context.
What is R438A?
R438A is an A1 retrofit refrigerant, also known as ISCEON MO99 or KDD5, used mainly for R22 systems.
What is the composition of R438A?
EPA composition tables show 8.5% R32, 45% R125, 44.2% R134a, 1.7% R600 and 0.6% R601a.
What is the GWP of R438A?
EPA SNAP tables commonly show 2,270.
Is R438A flammable?
No. It is classified A1.
What is R438A used for?
Primarily R22 retrofit work in legacy air-conditioning and refrigeration systems.
Is R438A a pure refrigerant?
No. It is a blend.
Why is R438A still important?
Because many legacy R22 systems are still in service and need practical retrofit guidance.
Is R438A future-proof?
No. It is mainly a practical transition refrigerant, not a modern low-GWP endpoint.
What is the trade name of R438A?
The best-known names are ISCEON MO99 and KDD5.
How should R438A leaks be detected?
Use leak detection suited to halogenated refrigerants and the intended maintenance or monitoring task.
Authoritative sources
Primary EPA references are prioritized, with supporting official or technical industry sources where helpful.
- EPA — Compositions of Refrigerant Blends
- EPA — Residential and Light Commercial Air Conditioning and Heat Pumps
- EPA — Industrial Process Air Conditioning
- EPA — Household Refrigerators and Freezers
- EPA — Regulations, Proposed Rules and Final Rules
- EPA — Status Change Rule 2 (higher-GWP context)
- CHE — Freon / ISCEON general refrigerants page
- GAS — GasNose Refrigerant Gas Library
Need help selecting or monitoring refrigerants?
Refrigerant choice is not only about GWP. Safety class, end use, machinery design, regulations and leak detection strategy all matter. If you are evaluating a transition project, ask for technical support.