Core: Refrigerants, Recovery & Safety: EPA 608 practice questions

The fact sheet says that because of the wide range in equipment types and designs, EPA does not issue retrofit procedures, and that the best source of information on how a given substitute will perform in a system is the manufacturer of the system and its components. EPA's SNAP review looks at risks such as ozone depletion, global warming potential, flammability and toxicity, but it does not determine whether an alternative will perform adequately or be compatible with system components. EPA's technician brochure adds that alternative refrigerants generally cannot be used as a "drop-in" without modifying system components.

The guideline states that HCFC refrigerants are partially miscible with mineral-based lubricants, while HFCs use more polar synthetic lubricants, and it pairs HFC refrigerants with polyolester (POE) lubricants in systems designed for them. That is why converting an HCFC-22 system to an HFC often means changing the oil from mineral oil to POE and then checking the remaining mineral oil content with a refractometer. The reversed pairing is wrong, and so are the two pairings that give both refrigerant families the same oil; the guideline notes only that adding hydrocarbons to HFCs may let some systems use mineral-based lubricants.

EPA's fact sheet "Ten Questions to Ask Before You Purchase an Alternative Refrigerant" notes lab data indicating that HCFC-22 is not compatible with XH-5 or XH-7 desiccant and can also damage NBR nitrile and HNBR rubber hoses and O-rings. It tells anyone considering a blend that includes HCFC-22 as a major component to ask about these issues before buying. EPA adds that it does not issue retrofit procedures, so the system and component manufacturers are the best source on how a substitute will perform.

Step 14 of the guideline's conversion procedure says that for blend refrigerants in the ASHRAE 400 series, technicians should remove liquid from the cylinder to ensure correct composition, and should make sure the liquid is vaporized before it reaches the compressor to avoid equipment damage. Taking vapor from the cylinder is not what the guideline prescribes for these blends, and letting liquid reach the compressor is exactly what it warns against. Composition also matters in EPA's SNAP review, which requires fractionation testing when a blend has a flammable component.

The guideline explains that ASHRAE 400-series refrigerants show temperature glide in the condenser and evaporator, meaning the dew point and the bubble point differ at a given pressure. It therefore uses the bubble point as the reference temperature when calculating subcooling and the dew point when calculating superheat, and tells technicians to get correct dew point and bubble point data from the refrigerant manufacturer. Using one point for both calculations, or swapping the two, gives the wrong reference for a blend with glide.

EPA's Ten Questions fact sheet explains that, as part of SNAP review, a new refrigerant must be tested by the ASTM E-681 method, which finds the concentrations in air at which a substance is flammable. In addition to testing the refrigerant itself, if a blend contains a flammable component, EPA requires fractionation testing to ensure that the composition of the blend does not change and become flammable. Keeping a blend's composition correct is also why EPA's GreenChill retrofit guideline says to remove 400-series blends from the cylinder as liquid.

Step 6 of the GreenChill leak-tight installation guideline says that if system pressure does not drop more than 1 psig from the initial test pressure within 24 hours, the system is ready to be evacuated, and it then says to release the nitrogen charge to the atmosphere, making sure there is adequate ventilation. This is consistent with 40 CFR 82.154(a)(1)(ii), which exempts nitrogen in any application from the venting prohibition. Only after the nitrogen is released does the guideline move on to evacuating the system, and refrigerant is charged after the evacuation steps.

The guidance says to store recovered refrigerant by refrigerant type, for example R-22, R-134a or R-1234yf, in separate refrigerant recovery cylinders, identifiable by a yellow band around the top collar of the recovery cylinder. Keeping one refrigerant per cylinder avoids mixing, and a separate junk container is used when the type is unknown. Green is the background color DOT requires on the NON-FLAMMABLE GAS hazard label, not the recovery cylinder marking EPA describes, and EPA's guidance does not describe red or white bands as identifying recovery cylinders.

Section 173.301(a)(6) says no person may fill a cylinder overdue for periodic requalification with a hazardous material and then offer it for transportation, but that prohibition does not apply to a cylinder filled prior to the requalification due date. The due date depends on the cylinder's specification under 49 CFR 180.209: Table 1 gives 4B, 4BA and 4BW cylinders a requalification period of 5, 7, 10 or 12 years depending on the conditions in 180.209(e), (f) and (j). An overdue cylinder must be requalified and marked before it is filled again.

The guideline says to weigh each cylinder once refrigerant is recovered and check the weight against maximum fill weights, and that the maximum gross weight, meaning the container plus its contents, must not be exceeded. Pressure does not show how much liquid a cylinder holds: DOT's 49 CFR 173.304a(c) requires liquefied gas to be filled by weight and allows a pressure–temperature chart only when the gas is lower in pressure than required for liquefaction. Waiting for a high-pressure cutout is not the guideline's check either; it says cylinder pressure must be monitored closely during compressor recovery, because overpressurizing can also release refrigerant or rupture the container.

Section 173.301(a)(8) sets the limit at 5/4 of the service pressure, not at the service pressure itself: the pressure of the hazardous material at 55 °C (131 °F) may not exceed 5/4 of the service pressure of the cylinder. The same paragraph requires sufficient outage so the cylinder will not be liquid full at 131 °F, and 173.304(b) says the liquid portion of a liquefied gas may not completely fill the packaging at any temperature up to and including 131 °F, with exceptions only for carbon dioxide, R-1132A, nitrous oxide and inhibited vinyl fluoride.

Section 178.65 is titled "Specification 39 non-reusable (non-refillable) cylinders," and paragraph (i)(2)(viii)(B) requires cylinders manufactured on or after October 1, 1996 to carry the statement "Federal law forbids transportation if refilled-penalty up to $500,000 fine and 5 years imprisonment (49 U.S.C. 5124)." The required markings say nothing about an 80 percent fill, a requalification interval or a label color; Specification 39 does not appear in the requalification table of 49 CFR 180.209, and a green background belongs to the NON-FLAMMABLE GAS hazard label under 172.415, not to the cylinder marking.

Section 84.116 applies from January 1, 2028 to disposable cylinders that contain a regulated HFC, were used in servicing, repair or installation, and will not be used again. Normally they must be sent to a certified reclaimer, a fire suppressant recycler, or a final processor or supplier able to remove the heel. Paragraph (e) lets a certified technician discard one directly to a final processor when the technician removed the heel, evacuated it to a vacuum of 15 in-Hg, and gives the final processor a signed certification statement. Zero psig, 10 in-Hg and 500 microns are not the level the rule names.

The 172.101 table lists Chlorodifluoromethane or Refrigerant gas R 22 in Division 2.2 with identification number UN1018. Under 49 CFR 173.115(b), Division 2.2 means a non-flammable, nonpoisonous compressed gas, including a liquefied gas, and the label table in 172.400 gives it the NON-FLAMMABLE GAS label; Division 2.1 is labeled FLAMMABLE GAS and Division 2.3 POISON GAS. R-22 is not listed in either of those, and Class 3 covers flammable liquids rather than gases. R-134a is likewise listed in Division 2.2, as UN3159.

The label table in 49 CFR 172.400(b) assigns the NON-FLAMMABLE GAS label, whose design is in 172.415, to Division 2.2, and the FLAMMABLE GAS label to Division 2.1. Section 172.415(b) requires the background color of the NON-FLAMMABLE GAS label to be green. The 172.101 table lists 1,1,1,2-Tetrafluoroethane or Refrigerant gas R 134a in Division 2.2 as UN3159, so a FLAMMABLE GAS label is wrong for it, and a red background is not the color 172.415 specifies for the NON-FLAMMABLE GAS label.

Section 82.152 defines a leak inspection as the examination of an appliance to determine the location of refrigerant leaks, using methods such as ultrasonic tests, gas-imaging cameras, bubble tests as appropriate, or a leak detection device operated and maintained to manufacturer guidelines. Methods that show only whether the appliance is leaking, such as standing pressure or vacuum decay tests, sight glass checks, receiver levels, pressure checks and charging charts, must be used with a method that can find the leak. Ultrasonic tests, bubble tests and gas-imaging cameras are listed as locating methods.

The guideline's safety section says not to use torches as leak detectors: old halide torches detect chlorine, which may not be present with new refrigerants, so technicians should use an electronic leak detector designed for the refrigerant in use. HFCs such as HFC-134a contain no chlorine. The guideline also warns that open flames release large quantities of acidic compounds in the presence of all refrigerants, and that these compounds can be hazardous.

The leak prevention checklist says to check the control line of every high-pressure switch about 12 inches from the compressor connection, because a temperature above the mechanical room ambient may indicate a leak in the control line, fitting or control bellows, and to log each rack's receiver level, because a drop from a previous reading may indicate a leak. Checking compressor oil levels monthly, checking motor and compressor amperage, and checking refrigerant lines for insulation decay appear instead in the fact sheet's separate list of other maintenance measures, which it presents as ways to keep systems operating efficiently and reduce wear and tear.

Step 6 of the guideline says to charge the system with regulated dry nitrogen, adding a tracer gas only if needed, and not to exceed system design pressures. The gas is specified dry because moisture left in a system causes expansion valve ice blockage, wax build-up and acid in the oil; shop compressed air is not the dry gas the guideline calls for. As a condition for GreenChill Store Certification, not a legal rule, HFCs may serve only as tracer gases when gases such as nitrogen or helium cannot achieve the required results. Oxygen is dangerous near oil, which refrigeration systems contain: OSHA's welding rules say a jet of oxygen must never strike an oily surface.

The guideline warns that nitrogen, air and moisture can remain in a system that is not properly evacuated, and that moisture causes expansion valve ice blockage, wax build-up and acid in the oil; EPA's retrofit guideline likewise says to evacuate to 500 microns to remove air and moisture. The other effects are tied in EPA's guidance to different causes: fractionation testing concerns blends that contain a flammable component, Viton is said not to perform well with R-134a, and lab data show HCFC-22 can damage NBR nitrile and HNBR rubber hoses and O-rings.

Among its pre-evacuation considerations, the guideline says copper lines are preferred over hoses, and any hoses used must be special vacuum hoses, because standard pressure hoses tend to collapse under high vacuum and increase the time required to fully evacuate the system. It also calls for a vacuum pump rated at 8 cubic feet per minute or larger, connected to several branch circuits, and for vacuum to be measured with a micron gauge at a minimum of two locations at the most extreme positions of the system.

The guideline's safety information says CFC, HCFC and HFC refrigerants are safe when handled properly, but any refrigerant can cause injury when mishandled. Hazards include liquid or vapor under pressure and frostbite from the escaping liquid, and overexposure to high concentrations of vapor can cause asphyxiation and cardiac arrest. It tells technicians not to work in areas with high concentrations of refrigerant vapor, to keep adequate ventilation, and not to breathe vapors or lubricant mists from leaking systems.

EPA's GreenChill retrofit guideline says not to use handheld leak detectors to check for breathable air, because these detectors are not designed to determine whether air is safe to breathe; oxygen monitors are used to ensure adequate oxygen is available to sustain life. The guideline also says to ventilate the area well after any leak before attempting to repair equipment. OSHA's respiratory protection standard treats an atmosphere with less than 19.5 percent oxygen by volume as oxygen deficient.

Section 1910.134(b) defines an oxygen deficient atmosphere as one with an oxygen content below 19.5% by volume, so 12.5, 16.0 and 18.0 percent all lie inside the deficient range rather than at its threshold. Under 1910.134(d)(2)(iii), all oxygen-deficient atmospheres shall be considered IDLH; the stated exception is that if the employer demonstrates the oxygen concentration can be kept within the Table II ranges under all foreseeable conditions, any atmosphere-supplying respirator may be used. For IDLH atmospheres the employer must provide a full facepiece pressure demand SCBA certified for at least thirty minutes, or a supplied-air respirator with an auxiliary self-contained air supply. EPA lists asphyxiation among refrigerant risks.

EPA's Refrigerant Safety page says exposure limits set for all chemicals are based on chronic toxicity concerns and are below the levels at which toxic effects were observed in laboratory tests; higher concentrations are allowable for short periods, but exposures should always be minimized. EPA defines chronic toxicity as the effects of repeated or sustained exposures over a long period, and notes that most chronic exposure indices are expressed as time-weighted average (TWA) values. Acute toxicity, the impact of single or short-term exposures, is used to gauge risks from accidental releases.

The guidance describes small appliances, sometimes called white goods, as including refrigerators, freezers, window air conditioners, vending machines and dehumidifiers, and notes that some may contain flammable hydrocarbon refrigerants, indicated by a warning label on the unit and red refrigerant tubing. EPA's R-22a page explains that a flammable refrigerant can burn or explode if enough of it is concentrated in one space and meets an ignition source. EPA's Refrigerant Safety page lists flammability alongside toxicity, asphyxiation and physical hazards.

Appendix B2, section 3.5, defines the push/pull method as transferring liquid refrigerant from a refrigeration system to a receiving vessel by lowering the pressure in the vessel and raising the pressure in the system, with a separate line connected between the system liquid port and the receiving vessel. The definition covers liquid, not vapor, and the pressures are arranged so the vessel is the lower-pressure side. Under 40 CFR 82.158(d)(8), certified recovery equipment has its liquid recovery rate and its vapor recovery rate measured separately under these appendices.