Indoor air pollution exists in varying degrees within homes, offices, laboratories, and industrial spaces. Airborne pollutants include:
- Nonconductive dust and fibers
- Conductive (i.e. metal) particles and fibers
- Corrosive gases
Ingress and accumulation of airborne pollutants inside product enclosures, and exposure to moisture and corrosive gases, can cause harm to electronic test and measurement equipment reducing its useful life. Exposure to very high levels of air pollutants can lead to unplanned downtime, product wearout and product failure. Accumulation of dust and metallic particles can increase the risk of electric shock and product fire.
Proper conditioning of air inside buildings, and proper maintenance of your test and measurement equipment maximizes user safety, product uptime and product longevity.
Pollution Degree Classifications
Industry standards specify “Pollution Degree” levels for various types of products and user applications. Pollution degree levels range from 1 to 4 as shown in Table I.
Per IEC 61010-1, Pollution Degree Level 2 is appropriate for indoor test and measurement equipment. In general, exposure to Pollution Degree Level 3 will require specially engineered protective measures, e.g. Ingress Protection (I.P.) enclosures or “hardening” of printed circuit assemblies through application of conformal coatings.
Table I. Pollution Degree Classifications
Pollution Degree Level
No pollution or only dry, nonconductive pollution. No impact on safety or product reliability. Can be achieved through the use of I.P. enclosures or hermetically sealed components.
Nonconductive pollution where occasional temporary condensation can occur. Generally applies to products used in homes, offices and laboratories.
Conductive pollution, or dry nonconductive pollution that can become conductive if condensation occurs. Generally applies to industrial applications. I.P. enclosures or PCA hardening techniques may be required for test and measurement equipment used in this environment.
Pollution that generates persistent conductivity, such as by rain, snow or metal particles. This level applies to outdoor environments; it is not applicable when the product standard specifies indoor use.
Forms of Airborne Pollutants
A) Nonconductive Dust and Fibers
Accumulation of dust and fibers can pose a risk to both equipment and user. Buildup of nonconductive particles on printed circuit assemblies (PCA’s), in combination with moisture, can increase the chance of electrical breakdown (arcing) between conductive elements and components. Arcing can increase the risk of electrical shock and product fire.
Proper thermal management is important to maximize reliability and product lifetime. Buildup of dust in fan screens and filters compromises proper airflow designed to ensure components operate within their specified temperature ratings. Similarly, buildup of dust on PCA components compromises thermal dissipation via conduction and convection. Elevated component temperature will shorten product life.
B) Metallic Particles
Metallic dust particles pose the additional risk of electrical short circuits. Common sources of conductive particles in office environments include motor brushes and paper shredders. Metallic pollutants can cause intermittent and permanent product failure.
C) Corrosive Gasses
Corrosive gases found in ambient air within office and industrial spaces include ozone, sulfur dioxide and nitrogen oxides (NOx). Ozone and NOx will react with certain plastic and rubber components, degrading product performance and useful product life. Sulfur dioxide can react with printed circuit board metallizations and component leads, resulting in oxidation, pitting, erosion and reduction in product performance or product failure.
Users of electronic test and measurement equipment can mitigate the risks brought on by indoor air pollutants by:
1) Employing proper HVAC practices to ensure site air is free of nonconductive dust, metallic particles and corrosive gases;
2) Regularly inspecting and cleaning of equipment screens and filters to ensure proper airflow within product enclosures; and
3) Performing regular preventive maintenance to ensure product circuitry is clean, free of dust and other particles, and free of damage caused by exposure to corrosive gases.
1) IEC 61010-1 (Safety Requirements for Electrical Equipment for Measurement, Control and Laboratory Use – Part 1: General Requirements); UL 61010-1 and EN 61010-1
2) IEC 60529 (Ingress Protection Marking)
By Bill Lycette, Quality Manager, Keysight Technologies, Inc.