Gravimetric impactors are perhaps the most widely used instruments for measuring fine particle size distribution, and their operating principle is well-known. Gravimetric impactors classify particles based on their aerodynamic diameter; the larger particles with more inertia are collected first in the topmost impactor stages, and the smaller particles with less inertia are collected downstream the gas flow. One of the benefits of the impactor size-classification method is the wide acceptance of the aerodynamic diameter in national and international standards as the definition of the particle size. In fact, most often the term PM10, PM2.5, or PM1.0 refers to particle aerodynamic size of 10 µm, 2.5 µm, or 1.0 µm respectively.
As an impactor collects the particles on different impactor stages, it enables both gravimetric and chemical analysis of the collected, size-classified particles. Therefore, impactors are the best choice when the mass size distribution and chemical composition of particles are of interest. Most Dekati® Impactors can also be used to sample hot gases, without the need to cool down the sample before the collection of the particles. In addition, Dekati® Low Pressure Impactor (DLPI+) and High Temperature DLPI+ work in low pressure, enabling the collection of very small particles all the way down to 16 nm. All the Dekati® Impactor designs are well characterized, and each manufactured instrument undergoes a thorough calibration to determine the exact cut points of the impactor stages.
Gravimetric measurement solutions
Dekati has a long tradition of providing high-quality gravimetric measurement solutions for a variety of applications, including ambient aerosol research, indoor and outdoor air quality measurements, occupational health & exposure measurements, stationary source emission measurements, and engine emission measurements, among others.
Dekati® gravimetric impactors
Cascade impactor comparison
|Particle size range||16nm-10µm||16nm-10µm||< 10µm||< 2.5 µm|
|Number of particle size|
|Number of impactor stages||Fixed||Fixed||Adjustable||Adjustable|
|Sample flow rate, lpm||10||10||10 or 30||50-100, adjustable|
|Max sample T, °C||50*||180*||200*||200*|
|Particle collection area||Ø25 mm||Ø25 mm||Ø25 mm, smallest particle size fraction on Ø47 mm filter||Ø47 mm, smallest particle size fraction on Ø70 mm filter|
|Additional||Can be upgraded to an ELPI®+/HT-ELPI®+/HR-ELPI®+||Can be upgraded to an ELPI®+/HT-ELPI®+/HR-ELPI®+||–||–|
* Can be increased up to 600 °C when combined with Dekati® Sample Conditioning Instruments