Test chambers background concentration

Smaller influence of chamber surfaces VOC test chamber background concentration may become a problem... 

After switching on (pre-operating phase), the emissions of the device increase and under the boundary conditions of the test (air exchange rate) an equilibrium concentration Cpre establishes on top of the background concentration Cbg of the emission test chamber. During the operating phase there occur the emissions from consumables and heated electronic components. Once the operation has... 

Chamber measurement Supply air quality Background concentration Sink effects/recovery Air exchange ratio Air tightness of the environmental test chamber Internal air mixing Air velocity Accuracy of temperature, RH and air exehange ratio Product loading factor... 

All the components of the chamber that are in direct contact with the inlet and outlet air and the chamber atmosphere have to be constructed in such a way that they emit no relevant amounts of VOC under test conditions and show only a very small sink effect (see 2.1.3.2). Suitable materials for the walls of a chamber are electro-polished stainless steel and glass. Seals are especially critical components. As little of their surface as possible should come into contact with the chamber atmosphere. Additional appliances such as fans are also problematical. The TVOC background concentration should be lower than 10 pg/m the background concentration of single compounds should be lower than 2 pg/m. ... 

By a continuous air current streaming in from outside, a defined air exchange rate is adjusted in the test chamber. The inlet air can be regulated most accurately by electronic mass flow controls. As inlet air, ultrapure synthetic air from pressure vessels or purified air from the surroundings can be used. The requirements of the purity of the inlet air follow from the permissible background concentration. 

Development of a suitable test chamber for evaluating the effects of submicron particles on indoor suifaces, including electronic equipment and devices, requires (1) the capability to produce suspended ionic particles that accurately simulate the composition and size distribution of airborne particles responsible for the observed effects (2) designing a chamber that combines continuous air-recirculation, filters out all background and once-through particles, and provides parallel airflow with miiform particle concentration over the flow cross section of the test area (3) fabrication and evaluation of suitable test samples or devices and... 

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