DioxinMonitoringSystem® uses the dilution method of the standard EN 1948-1 standard. Many advantages underline the
versatile use of this method.
The dilution method used in our device avoids condensation, whereas the cooled probe method and the
filter/condenser method condense the humidity inside the filter/adsorber. Refering to EN 1948-1, this condensate has
to be collected and transferred completely to the laboratory. e.g. sampling of 1 m3/hour at 20% humidity
produce 4 liters of condensate in 1 day, 28 liters in 1 week and consequently 108 liters in one month. The dilution
method condenses no humidity. Therefore a dry cartridge is transferred to the laboratory.
Complete sampling of the dust fraction
The EN 1948-1 standard requires the precipitation of the fine dust fraction with better than 99,5%
as a minimum requirement. The dilution method uses a dry filter at 40°C temperature, precipitating all dust
particles. The fine dust fraction < 2,5 µm is precipitated with very high efficiency.
New investigations in Germany have shown, that in modern municipal waste incineration plants the
portion of the fine dust fraction is higher than 60%. Other long term sampling devices for dioxins use wet wool for
dust precipitation, which is not sufficient, because fine dust can pass the cartridge, precipitated dust can be solved
only and washed through the cartridges.
Low sampling temperature
In flue gas, dioxins are adsorbed to activated carbon and fine dust particles and evaporated in the
gas phase. By cooling the flue gas with dilution air, a high portion of the gaseous dioxins are adsorbed by the
particles, thus, most of the dioxins are precipitated on the dust filter at the temperature of 40°C. At this low
temperature, no further reactions (losses) or denovo synthesis (formation) are possible.
Two measurement positions compared to traversing
EN 1948-1 requires representative sampling. For highest accuracy, traversing shall be done
according EN 13284-1, using 4, 9 or 16 positions in the stack. EN 1948-1 allows the use of two measurement positions
instead of traversing. In this case (two positions instead of traversing) the measurement uncertainty has to be
increased by 10% (part 3, Annex B.3).
The dilution method is a complex method, which needs many adjustments during measurement. The
DioxinMonitoringSystem® provides these adjustments automatically - accurate I-TEQ values are the result.