EPA 608 Study Guide: The Numbers That Actually Get Tested
Two tables account for a large share of the questions people fail on — required evacuation levels and leak-rate thresholds. Both are widely republished incorrectly. The figures below are quoted from the regulation itself and from EPA, not from other study guides.
Start Here: Two Rules Most Guides Get Wrong
The "4 inches under 200 lb, 23 inches over" rule is not in the regulation
A very widely republished study-guide rule says 'evacuate to 4 inches Hg if the appliance holds under 200 pounds, 23 inches Hg if it holds 200 pounds or more.' That is not what Table 1 says. The required level depends on the appliance's pressure class as well as its charge size, and on whether the recovery equipment was manufactured before or on/after 15 November 1993. Several classes require 0 inches Hg, and low-pressure appliances are specified in millimetres of mercury absolute rather than inches of vacuum.
The industrial process leak threshold is 30%, not 35%
Many prep sites still publish the pre-2016 thresholds of 15% for comfort cooling and 35% for both commercial and industrial process refrigeration. EPA lowered all three; the industrial process figure is now 30%, not 35%.
Required Evacuation Levels
The vacuum an appliance must be evacuated to before it is opened for major repair, when refrigerant is not being isolated in a sealed portion of the system.
Source: 40 CFR 82.156, Table 1 — Required Levels of Evacuation for Appliances. Table 1 splits every row by whether the recovery or recycling equipment was manufactured before 15 November 1993, or on/after that date. Equipment made on or after the cutoff must generally pull a deeper vacuum.
| Appliance | Charge | Equipment made before 15 Nov 1993 | Equipment made on/after 15 Nov 1993 |
|---|---|---|---|
| Small appliances Small appliances are the exception to the vacuum-only rule: the regulation allows recovery of a specified percentage of the charge — the required percentage depends on whether the appliance's compressor is operating — as an alternative to evacuating to 4 inches of mercury vacuum. | Factory-sealed, 5 lb or less | 80% or 90% recovery, or 4 in Hg | 80% or 90% recovery, or 4 in Hg |
| High-pressure appliance A frequent exam trap: the most common service scenario requires no vacuum at all, only that the system be brought to atmospheric pressure. | Less than 200 lb | 0 in Hg | 0 in Hg |
| High-pressure appliance | 200 lb or more | 4 in Hg | 10 in Hg changes |
| Very high-pressure appliance Pulling a deep vacuum on a very high-pressure refrigerant is not required; the level is 0 inches Hg regardless of equipment age. | Any charge | 0 in Hg | 0 in Hg |
| Medium-pressure appliance | Less than 200 lb | 4 in Hg | 10 in Hg changes |
| Medium-pressure appliance | 200 lb or more | 4 in Hg | 15 in Hg changes |
| Low-pressure appliance Specified as an absolute pressure in millimetres of mercury, not as inches of vacuum — the one row on the table that changes units. This is the Type III figure most often missed. | Any charge | 25 mm Hg absolute | 25 mm Hg absolute |
Memorise these 3 rows first. They are the only ones where the answer changes with the age of your recovery equipment, which makes them the rows exam questions are built from — the question has to tell you the equipment date, and that tells you it matters.
Leak Rate Thresholds & Repair Deadlines
Appliances with a full charge of 50 or more pounds of ozone-depleting refrigerant.
Comfort cooling
Superseded figure still printed elsewhere: 15%
Commercial refrigeration
Superseded figure still printed elsewhere: 35%
Industrial process refrigeration
Superseded figure still printed elsewhere: 35%
Repair deadlines
| Situation | Deadline |
|---|---|
| Standard repair | 30 days from the date the leak was discovered |
| Retrofit or retirement instead of repair | Plan developed within 30 days, completed within 1 year |
| Industrial process refrigeration requiring a process shutdown | 120 days substituted for the normal 30-day period |
Reporting trigger: Owners and operators must report to EPA when an appliance containing 50 or more pounds leaks 125% or more of its full charge in one calendar year.
What counts as repaired: A repair only has to bring the annual leak rate back below the applicable threshold — it does not have to eliminate the leak entirely.
Common Questions
What vacuum do I need to pull before opening a system?
It depends on the appliance, not on one universal number. A high-pressure appliance holding less than 200 pounds requires 0 inches of mercury vacuum — atmospheric pressure is enough. A high-pressure appliance holding 200 pounds or more requires 10 inches Hg if your recovery equipment was made on or after 15 November 1993, or 4 inches if it was made before. Low-pressure appliances are specified differently again, at 25 mm Hg absolute. The full table is above.
Is the required evacuation level really 4 inches Hg under 200 pounds and 23 inches over?
No, and this is the single most republished error in EPA 608 prep material. That rule does not appear in the evacuation table at 40 CFR 82.156. The regulation splits requirements by pressure class — small, high, very high, medium, low — as well as by charge size, and several classes require 0 inches Hg. If a practice test marks you wrong for answering 0 on a high-pressure appliance under 200 pounds, the practice test is wrong, not you.
What are the current leak rate thresholds?
For appliances with a full charge of 50 or more pounds of ozone-depleting refrigerant: 10% annually for comfort cooling, 20% for commercial refrigeration, and 30% for industrial process refrigeration. Many study guides still print the superseded figures of 15% and 35%. EPA lowered all three, and the industrial process threshold is now 30%, not 35%.
How long do I have to fix a leak that exceeds the threshold?
30 days from the date the leak was discovered. Alternatively you can develop a retrofit or retirement plan within 30 days and complete it within one year. Industrial process refrigeration that requires a process shutdown to reach the leak gets 120 days instead of 30. A repair only has to bring the annual leak rate back below the threshold — it does not have to eliminate the leak entirely.
Why does 15 November 1993 keep appearing in the answers?
That is the cutoff date built into the evacuation table itself. Recovery and recycling equipment manufactured on or after 15 November 1993 must generally pull a deeper vacuum than older equipment. So the same appliance can have two different correct answers depending on the age of the machine you are recovering with, which is exactly why exam questions specify it.
Sources
Both tables on this page were read from the primary text on the access dates below — the evacuation table from the Code of Federal Regulations itself, the leak-repair figures from EPA. We deliberately did not copy them from other study guides, because the republished versions of both tables are commonly out of date.
- 40 CFR 82.156 — Required practices (Table 1: Required Levels of Evacuation for Appliances), eCFR. Accessed 4 August 2026.
- Stationary Refrigeration Leak Repair Requirements — US EPA. Accessed 4 August 2026.
- Regulatory Updates: Section 608 Refrigerant Management Regulations — US EPA. Accessed 4 August 2026.
Figures reviewed 4 August 2026. HVACTechTest is an independent study resource and is not affiliated with, endorsed by, or sponsored by the U.S. Environmental Protection Agency, ESCO Institute, or any certifying organization.
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