Domnick Hunter coalescing filter grades are typically identified by suffixes. Filter grades such as AO, AA, AC, and ACS are widely used in compressed air systems, but it can get confusing when it comes to performance and compatibility.

This guide explains what each filtration grade does, how Domnick Hunter part numbers work, and the important difference between 030AA separator-style filters and K-series elements.

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How Domnick Hunter Part Numbers Work

Most Domnick Hunter elements follow a simple format:

Size + Grade

• 030AO
• 030AA
• P030AA
• K060AO
• K060AA

• Size (030, 060, etc.) → housing size / flow capacity
• K prefix → K-series element style
• Grade (AO, AA, AC, ACS) → filtration function

The size does not represent physical length. It corresponds to flow capacity and housing design.

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Domnick Hunter Filter Grades Explained

Grade	Function	Typical Use	Stage
AO	General purpose coalescing	Bulk oil aerosol removal	Pre-coalescing
AA	High efficiency coalescing	Fine oil aerosol removal	Final coalescing
AC	Activated carbon	Oil vapor removal	Carbon stage
ACS	Enhanced carbon filtration	Critical air / odor removal	Final carbon stage

What About AR Filter Grade?

The AR grade is used for fine particulate removal and is typically installed downstream of coalescing filters in applications requiring extremely clean, dry air.

• AR → Fine particulate filtration
• Often used after AA filters
• Helps remove solid contaminants from dried air

Not all systems use AR filters, and availability may vary depending on housing style and application.

Important: Domnick Hunter grades are defined by part number, not color.

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Two Different Domnick Hunter Filter Styles (Do Not Mix Up)

One of the most common mistakes is assuming all AO or AA filters are physically the same. They are not.

Style	Examples	Description	Crosses To
Inline / Separator Style	030AA, P030AA	Separator-style design with top inlet	Finite, CompAir, FS-Curtis, Sullair
K-Series Element Style	K030AO, K030AA, K030ACS	Standard element-style filter	Walker, Nano (by function)

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What Does TS Mean (AO-TS / AA-TS)?

TS versions are designed for higher operating temperatures.

• AO = standard coalescing
• AO-TS = high temperature version
• AA = high efficiency
• AA-TS = high temperature version

TS refers to temperature capability, not mounting style.

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How to Visually Identify AO, AA, AC, and ACS Filters

• AO → often darker/red media or white (varies)
• AA → typically white media
• AC → carbon-filled element
• ACS → perforated outer shell

Note: Always confirm the part number.

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030AA vs P030AA

P030AA is commonly used as a newer Parker designation for the 030AA series. In most applications, they are functionally equivalent.

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Typical Filtration Setup

• AO → pre-coalescing
• AA → high efficiency coalescing
• AC → vapor removal
• ACS → final polishing stage

Coalescing filters remove liquid oil. Carbon filters remove vapor.

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Quick Cross Reference by Function

Function	Domnick	Nano	Walker
General coalescing	AO	M5 / M1	A
High efficiency	AA	M01	AA
Vapor removal	AC	AC	ACS
Final stage	ACS	AC	ACS

Final Thoughts

The biggest mistake is assuming all AO or AA filters are the same design. The 030AA filter has a unique, rather tall black top inlet. The K030AA filter looks more like a standard coalescing filter with a very short top inlet. Some K Series elements have a cone-shaped bottom with ridges. Always match both the style and the grade.