RAS 3000

Reference aerosol distributor for protection degree determination and/or calibration of particle counters


Brief Description
Brief product description in two-pages as PDF
Product Description
Detailed product description as PDF
RAS_3000_neu.jpg (2)

RAS 3000

Reference aerosol distributor for protection degree determination and/or calibration of particle counters



The RAS system comprises an aerosol generator, a liquid heating unit, a thermocouple to measure the temperature, and an aerosol distributor with six outlets. Six outlet cylinders are connected to these outlets on the aerosol distributor by means of hose connections. The liquid to be nebulized, e.g. DEHS, is able to be heated.

The highly accurate aerosol concentration is obtained by means of a special aerosol generator and one mass flow controller each for the generator and for the mixed air.

The RAS 3000 enables a defined aerosol to be generated with the required reference source flow (QRef ) at six different points simultaneously within the operating room for protection degree determination (SG) as per SWKI 99-3 and DIN 1946-4. The RAS 3000 features the option to rapidly and reproducibly adjust the reference source flow (QRef).

Why is protection degree determination necessary?

An operating room is a special place intended to protect the patient and personnel against contamination. Different ventilation systems can be used to keep the air clean. The efficacy of these ventilation systems must be reproducibly verifiable within the operating room.

Purpose of protection degree determination

The air quality in operating rooms is quantitatively and reproducibly determined by measuring the air purity around the operating table during a defined contamination process in any operating room.

The six aerosol feeding cylinders (AAZs) of the RAS 3000 have a perforated cylinder wall, as required by the standard. The decisive advantage of the RAS 3000 is the option to reliably monitor the source flow (QRef) at all six AAZs with any suitable optical particle counter (OPC). During this process, the maximum concentration difference at the six AAZs is 4%. The same is true for the variation in particle concentration during a measuring period of three hours, for example.

Clear and reproducible protection degree determination

Six standard test conditions enable a clear, quantitative, and reproducible protection degree determination with

1. Protection ratio 1: 105

2. Reference concentration Cn,Ref = 106 P/ft3 = 35.3 • 106 particles/m3

3. Reference source flow QRef = 6.3 • 109 P/min

4. Positioning of source sites with defined outflow

5. Arrangement of two sample loads within protection area

The protection degree (SG) is calculated with the following equation:

SG = -log (C/Cn,Ref).

Cn,Ref is the reference concentration, which is predefined as 1: 105 based on the specified protection ratio.

QRef, the reference source flow, is defined in the standard in order to be able to contaminate and compare different operating rooms with the same particle amount per time unit.

Sample loads

The standards specify two different types of loads:

1. Sample load 1: Load induced from outside

2. Sample load 2: Load induced from inside

Skizze Musterlast.JPG


TAV = Low-turbulence displacement flow 

MP = Measuring point for OPC 

RAS 3000 = Reference aerosol system 

AAZ = Aerosol feeding cylinder

The reference source flow QRef must be measured in the OP because the ISO 21501-4 standard allows the lower counting efficiency of particle counters to vary by ±20% and the volume flow to vary by ±5%. Consequently, measurement results obtained using these tolerances may differ by about 50%.


The reservoir must be filled with the fluid to be dispersed and the six outlet cylinders must be connected to the aerosol distributor using six hoses. The RAS 3000 is equipped with a compressed air connection to generate the required volume flow on the aerosol generator and the required dilution air during operation. The corresponding volume flows are adjusted by means of mass flow controllers on the device.

As an alternative to compressed air, the ACA 1000 adjustable clean air station can also be used.


Fig. 1: ACA 1000

ACA 1000 adjustable clean air station to supply the RAS 3000 with clean air:

1. Compressed air in combination with the RAS 3000: When using this configuration, it must be ensured that the supplied compressed air is dry and free of particles and oil.

2. ACA 1000 in combination with the RAS 3000: Only one electrical outlet is required. The ACA 1000 uses the air in the operating room and filters it with an H14 filter element. The volume flow is adjustable up to 335 L/min.

In addition, the RAS 3000 can also be used to calibrate optical particle counters, see also the RAS 3000 C model version.

Calibration of optical particle counters

Depending on the application, very low aerosol concentrations are able to be generated for the calibration of optical particle counters with Cn, max = 4 particles/cm3 = 4 • 106 particles/m3. This enables optical particle counters as per ISO 21501-4 to be calibrated economically and reproducibly without aerosol dilution.


  • Defined aerosol generation
  • Consistent aerosol distribution across six aerosol feeding cylinders (AAZs)
  • Easily adjustable reference source flow (QRef)
  • Perforated cylinder wall of the AAZs (see SWKI 99-3)
  • Quick comparison between the counting rates of up to six particle counters
  • Easy to connect a particle counter up to 28.3 L/min to the six AAZs
  • Low maintenance
  • Easy to operate
  • Reliable function 


Volume flow 3.8 l/min
Power supply

115 – 230 V, 50 – 60 Hz
approx. 490 mm • 300 mm • 240 mm
approx. 10.7 kg
Particle size range
< 0.1 – 2 µm
Aerosol outlet connection
Øinside = 9 mm, Øoutside = 12 mm
Filling quantity 300 ml


  • Protection degree determination in operating rooms as per SWKI 99-3 and DIN 1946-4
  • Clean room acceptance tests
  • Calibration of measuring devices with the RAS 3000 C

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