Standard Clarity
IEC 60664-1

Pollution Degree 1-4 Selector

Choose the conditions that can reach the insulating surface. The result updates as you go and gives you a conservative IEC 60664-1 starting point for creepage design.

Maintained byGiorgi Gaprindashvili Published Updated Technical review

Interactive selector

Choose the conditions at the insulation

Start with a typical case or adjust the three groups yourself. The result updates immediately.

Quick startExamples only - review every selection before using the result.
PD2
Current result

Pollution Degree 2

Mostly non-conductive contamination

Adjust the environment choices to update this result.

What reaches the insulation? Choose what can actually reach the insulating surface during normal service.

Can moisture appear? Include start-up, shutdown, cooling and unheated periods.

What protection is verified? Choose the protection that is actually justified for this construction.

Method based on IEC 60664-1 Ed. 3.1 (2020 + Amendment 1:2025) and IEC 60664-3:2016 · reviewed August 2026 · method microenvironment decision tree · revision 2.1

How the four pollution degrees differ

conductivity at the insulation surface increases from left to right 1 Clean, dry no effectivepollution 2 Temporary non-conductive dust+ brief condensation 3 Expected conductive pollutionor recurrent condensation 4 Persistent wet conductive filmdoes not clear classify the microenvironment at the insulation, not the building as a whole
The key change is conductivity at the insulating surface: clean and dry, briefly conductive, regularly conductive, then persistently conductive. The local condition can differ from the surrounding room when the protection is properly designed and verified.

Pollution Degree 1-4 at a glance

Classify the immediate area around the insulation. The examples below are practical cues, not automatic classifications for every product.

DegreeWhat is happening at the surfaceTypical clueWhat it means for the design
PD1 The insulation stays clean and dry, or dry contamination has no effect A sealed, verified clean area The shortest creepage values may apply where the product standard allows it
PD2 Contamination is non-conductive; brief condensation can make it temporarily conductive Dry dust or occasional condensation Use PD2 creepage values and verify the condensation assumption
PD3 Conductive contamination is present, or recurring dampness makes dry contamination conductive Metallic or salt residue, recurrent condensation Longer creepage and stronger environmental control are usually needed
PD4 The surface can remain conductive because of rain, wetness or conductive dust Persistent wet film or direct weather exposure Reduce the pollution at the insulation or use a product-specific method before spacing design
Pollution degree belongs to the insulation microenvironment. A well-designed enclosure, heater, seal or qualified protective system can make the internal condition different from the room or outdoor environment.

Classify the surface, not the room

Pollution degree applies to the immediate area around the insulation path. A factory can contain a clean, controlled cabinet, while an indoor product can still suffer condensation at a cold wall, connector or PCB edge.

Use the worst credible condition in normal service. Include temperature cycling, shutdown periods, conductive process dust, salt residue, cleaning fluids and moisture that can remain on the surface.

The practical boundary between PD2 and PD3

PD2 fits dry, non-conductive contamination where any conductivity is brief and tied to occasional condensation. PD3 applies when contamination is conductive by itself, or when dampness is expected often enough to make dry deposits conductive as part of normal service.

Do not classify a product from the industry name alone. An industrial cabinet can contain a PD2 internal microenvironment, while an unheated indoor product can reach PD3 if dust and recurring condensation meet at the insulation.

Coating and potting only count when they are qualified

IEC 60664-3 covers permanent protection by coating, potting or moulding. A qualified protective system can establish a cleaner microenvironment, but only when the materials, coverage, manufacturing controls and tests support that claim.

An ordinary enclosure or an unspecified conformal coating is not enough to select PD1. Check ageing, adhesion, coverage, repair limits and the requirements of the product standard.

How the result affects creepage design

Pollution degree is one of the inputs used to select creepage distance and, in some cases, a minimum clearance floor. As the surface becomes more likely to conduct, the required surface path generally increases.

For PD1 to PD3, carry the result into the Creepage and Clearance Calculator, then verify the spacing against the applicable product standard. PD4 usually calls for better environmental protection or a product-specific construction and test method.

Worked classification examples

These examples show how the immediate insulation environment drives the result. Product standards and verified protective systems can change the final classification.

MicroenvironmentLikely resultWhy
Sealed sensor cavity with verified permanent protectionPD1 candidateThe insulation area stays clean and dry, and the protective system is qualified for the construction.
Office or laboratory equipment with dry dust and occasional condensationPD2The contamination is non-conductive and any conductivity is temporary.
Unheated industrial cabinet with dust and recurring condensationPD3The deposits are expected to become conductive during normal service.
Exposed terminals subject to rain or a persistent conductive filmPD4The surface can remain conductive and needs environmental protection or a product-specific method.

Where engineers use this classification

Pollution degree is an insulation-coordination input, not a general score for how clean or dirty a location feels.

PCB creepage design

Choose the pollution degree before using creepage tables for mains, DC-bus and isolated circuits.

Industrial controls

Check whether dust, coolant mist and unheated shutdown periods create a PD2 or PD3 condition inside the panel.

Outdoor equipment

Separate the weather outside the enclosure from the actual condition at the internal insulation path.

Coated or potted assemblies

Confirm that the protection is qualified under IEC 60664-3 instead of assuming any coating creates PD1.

This selector is a conservative screening aid. The applicable product standard, certification construction, enclosure design and verified protective system determine the final pollution degree and spacing requirements.

Frequently asked questions

What is pollution degree in IEC 60664-1?
It is a numeral describing the expected pollution of the microenvironment around electrical insulation. The four degrees run from clean and dry conditions at Degree 1 to persistent conductivity from conductive dust, rain or other wet conditions at Degree 4. It is used when determining creepage and clearance requirements.
What is the difference between Pollution Degree 2 and 3?
Degree 2 normally has only non-conductive pollution, with temporary conductivity possible from occasional condensation. Degree 3 has conductive pollution, or dry non-conductive pollution that is expected to become conductive because condensation or dampness recurs.
Is Pollution Degree 2 always an indoor environment?
No. Pollution degree applies to the insulation microenvironment, not simply indoor versus outdoor. An enclosure can create a PD2 condition inside an outdoor product, while an unheated indoor product can reach PD3 if contamination and recurrent condensation are expected.
Does an IP rating determine the pollution degree?
No direct one-to-one conversion exists. An enclosure's IP rating can help control dust and water entry, but pollution degree depends on the actual microenvironment, condensation, conductive deposits, openings, maintenance and the applicable product standard.
Does conformal coating automatically make a design Pollution Degree 1?
No. IEC 60664-3 defines qualified permanent protection by coating, potting or moulding. A Type 1 protective system can improve the protected microenvironment to PD1 only when the construction and tests meet the standard. An unspecified coating is not enough.
Can I use Pollution Degree 4 in an ordinary creepage calculator?
Not as a routine PD1-to-PD3 table choice. PD4 describes persistent conductivity and normally requires reducing the pollution at the insulation through suitable protection, or following a product standard that defines a specific construction and test method.
Which pollution degree should I use if my product standard specifies one?
Use the applicable product standard. This selector can help check whether the environmental assumptions are sensible, but it cannot override a pollution degree, enclosure condition or test requirement assigned by the product standard.
What is the current edition of IEC 60664-1?
The current consolidated base publication is IEC 60664-1:2020 with Amendment 1:2025, Edition 3.1. Verify the edition required by the product standard and certification scheme used for your equipment.

Related tools and standards

Creepage & Clearance CalculatorUse the selected PD1, PD2 or PD3 in the insulation-spacing calculation.IEC 60664-1 explainedSee how pollution degree, voltage, CTI and overvoltage category fit together.Enclosure & Safety CalculatorsBrowse ingress, insulation and material-safety tools.NEMA Enclosure Type SelectorChoose an enclosure type for dust, water, corrosion and washdown exposure.IP / NEMA Rating DecoderDecode ingress ratings without treating them as a pollution-degree conversion.

References

Use the current edition required by the product standard or certification scheme for the equipment.