What Is Vapor Degreasing and How Does a Vapor Degreaser Work?

How does vapor degreasing clean parts?

Vapor degreasing cleans parts by condensation: a vapor degreaser boils a solvent, and the hot vapor condenses on the cooler parts, dissolving and lifting oils, greases and fluxes (MicroCare, accessed 2026). A typical batch cycle has four moves. The operator or hoist lowers the basket into the vapor above the boil sump, where condensation starts the cleaning. The basket then goes into the boiling solvent, where the tumbling liquid reaches tight spaces and does the heavy cleaning. Next it moves to the rinse sump, which holds freshly distilled solvent, and finally it rises slowly back through the vapor and out of the machine (MicroCare, accessed 2026).

Vapor that reaches the cooling coils condenses, passes through a water separator and flows into the rinse sump, which overflows into the boil sump (MicroCare, accessed 2026). Contamination removed from parts becomes concentrated in the boil sump, while the rinse sump always holds freshly distilled fluid (MicroCare, accessed 2026). MicroCare describes the result as a fluid that can be used hundreds or thousands of times before it needs replacing (MicroCare, accessed 2026).

What do the boil sump, vapor zone and freeboard do in a degreaser?

In a vapor degreaser, the boil sump makes the vapor, the vapor zone does the cleaning and the freeboard keeps the vapor inside the machine. Heating coils under the boil sump bring the solvent to its boiling point, and the saturated vapor fills the space above both sumps (MicroCare, accessed 2026).

The vapor zone ends at the primary condenser, a ring of cooling coils that continuously condenses rising vapor to create a concentrated vapor zone (40 CFR 63.461, 2026). US rules define the solvent/air interface of a vapor degreaser as the mid-line height of those coils (40 CFR 63.461, 2026). A vapor degreaser covered by the US halogenated solvent rule that follows its equipment standards, rather than the alternative emission limits in 40 CFR 63.464, needs a primary condenser and a vapor level control that shuts off sump heat if vapor rises above it (40 CFR 63.463, 2026).

Freeboard height is the distance from the solvent/air interface to the top of a batch machine, and freeboard ratio is that height divided by the smaller interior dimension of the machine (40 CFR 63.461, 2026).

What solvents are used for vapor degreasing?

Vapor degreasing uses solvents that boil at moderate temperatures and condense easily on cooling coils. Long-used halogenated solvents include TCE, which boils at 87.2 °C, and PCE, which boils at 121.2 °C (PubChem, 2026). n-Propyl bromide (nPB, 1-bromopropane) boils at 71 °C at 760 mm Hg (PubChem, 2026). MicroCare states that its engineered vapor degreasing fluids usually boil between 40 °C (105 °F) and 65 °C (165 °F), depending on the formulation (MicroCare, accessed 2026).

The halogenated solvent cleaning NESHAP covers machines whose solvent holds more than 5% by weight of methylene chloride, PCE, TCE, 1,1,1-trichloroethane, carbon tetrachloride or chloroform, alone or combined (40 CFR 63.460, 2026). EPA added nPB to the Clean Air Act list of hazardous air pollutants effective 4 February 2022, and said then that no NESHAP set standards for it (EPA, 2022). As of 2026-10-15, EPA's December 2024 TSCA rule prohibits most uses of TCE, with longer phase-outs under worker protections for some parts cleaning, such as aircraft and medical device parts (EPA, 2026). EPA's December 2024 PCE rule lets PCE use as a vapor degreasing solvent continue under a Workplace Chemical Protection Program, whose compliance dates EPA extended in July 2026 (EPA, 2026). EPA has opened reconsideration of the PCE rule and of elements of the TCE rule (EPA, 2026). Check EPA's current TSCA rule pages and the solvent's safety data sheet (SDS) for exposure limits before choosing or changing a solvent.

Why do parts come out of a vapor degreaser dry?

Parts come out of a vapor degreaser dry because the low-boiling solvent left on them drains back into the machine or evaporates before they leave the freeboard. MicroCare describes parts leaving the machine clean, dry and cool to the touch, ready for the next step (MicroCare, accessed 2026). Condensation needs a part cooler than the vapor, so a part at vapor temperature no longer collects fresh liquid (our inference, not a sourced rule).

Dwell means holding parts in the freeboard, above the vapor zone, after cleaning so solvent can drain back into the machine (40 CFR 63.461, 2026). Where a degreaser uses dwell to comply, the dwell time must be at least 35% of the time a room-temperature part takes to stop dripping in the vapor zone (40 CFR 63.465, 2026). A superheated vapor system goes further: it heats the vapor above the solvent's boiling point and holds parts in it to evaporate the liquid solvent before they exit (40 CFR 63.461, 2026). Slow removal matters too, and the US rule requires a hoist capable of moving parts at 3.4 m/min (11 ft/min) or less (40 CFR 63.463, 2026).

Typical vapor degreasing temperatures and freeboard values

Typical vapor degreasing values come from two places: the solvent's boiling point sets the sump temperature, and US emission rules set freeboard and control values. The table below gives each zone of a batch vapor degreaser and what its value means. The freeboard and chilled air values are US requirements for machines using the listed halogenated hazardous air pollutant (HAP) solvents that follow the equipment standards of 40 CFR 63.463; for other solvents they are a reference, not a legal limit. The TCE, PCE and nPB rows are pure-solvent boiling points; blends take theirs from the technical data sheet (TDS).

The key row for most buyers is freeboard ratio: a US batch vapor degreaser on a halogenated HAP solvent needs at least 0.75, and 1.0 when its chosen control combination includes a freeboard ratio of 1.0 (40 CFR 63.463, 2026), unless it meets the alternative emission limits in 40 CFR 63.464 instead.

What is the difference between vapor degreasing and cold cleaning?

Vapor degreasing boils the solvent and cleans with its vapor, while cold cleaning cleans parts in liquid solvent that does not boil. US rules define a cold cleaning machine as equipment that contains or uses liquid solvent into which parts are placed to remove soils or to dry them, and they classify machines using heated, nonboiling solvent as cold cleaning machines (40 CFR 63.461, 2026). A vapor cleaning machine, by contrast, boils liquid solvent and uses the vapor as part of the cleaning or drying cycle (40 CFR 63.461, 2026).

A cold cleaner leaves parts wet with liquid solvent; under the US NESHAP, a batch cold cleaner that uses a freeboard ratio of 0.75 or a remote reservoir must drain parts for 15 seconds or until dripping stops, whichever is longer (40 CFR 63.462, 2026). A vapor degreaser rinses in freshly distilled solvent and returns parts dry, because the machine distills its own solvent continuously (MicroCare, accessed 2026). Both fall under the US NESHAP when the solvent holds more than 5% by weight of a listed halogenated solvent (40 CFR 63.460, 2026). Lubinpla can compare a vapor degreasing and a cold cleaning option from your own TDS, SDS and site history and return one cited document for your review.

Related terms

• Primary condenser: the cooling coils that set the top of the vapor zone.

• Freeboard ratio: freeboard height divided by the smaller interior dimension of the machine.

• Dwell: holding parts above the vapor zone so solvent drains back.

• Superheated vapor system: vapor heated above the boiling point to dry parts before exit.

• Cold cleaning: cleaning in nonboiling liquid solvent.