AQ Guard

Air quality analyzer for monitoring indoor air quality of fine dust from a particle size of 0.15 µm, measurement of CO2, TVOC, calculation of air quality index and infection risk indicator


AQ Guard: Messgerät, Überwachung Luftqualität Innenräume, Feinstaubmessung

AQ Guard

Air quality analyzer for monitoring indoor air quality of fine dust from a particle size of 0.15 µm, measurement of CO2, TVOC, calculation of air quality index and infection risk indicator

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AQ Guard, currently the most advanced compact analyzer for determining indoor air quality, continuously and reliably analyses airborne fine dust particles in the range 0.175 – 20 µm (*1 IAHP-Package starting from 0.15 µm). A newly developed mass conversion algorithm calculates PM values based on single particle optical light scattering, taking signal duration and shape into account. Sensor system and algorithms were developed based on the technology of the EN 16450 certified Fidas® 200.

Comparison measurements

Vergleichsmessung Fidas AQ Guard.jpg

Fig. 1: Comparison of data recorded by AQ Guard and Fidas® 200 S

The high correlation values of the AQ Guard to the reference Fidas® 200 confirm the comparability of both systems.

Operating principle

AQ Guard simultaneously calculates and records PM1, PM2,5, PM4, the total dust load, the particle number concentration CN as well as the particle size distribution. AQ Guard thus provides precise and comprehensive information about indoor particulates as only a single particle counting and sizing device can.

The device is designed for unattended, continuous operation and features an extraordinarily durable sampling gas blower. Aerosol sampling as well as optical sensor system resist staining but can be cleaned, if necessary, by the user.

Exceptional long-term stability of the measuring system is achieved by automatic calibration tracking and allows up to two years of operation without recalibration. Calibration status can be checked, using a test powder calibrated by Palas®. This makes Palas® aerosol spectrometers the only optical fine dust monitors which can be readjusted by the user with a traceable standard on site.

Auxiliary sensors for CO2 and volatile organic carbohydrates (TVOC) built into AQ Guard provide data for calculating an indoor air quality index (AQI) according to the European model. AQ Guard also records air temperature, pressure and relative humidity.

Since CO2 is a tracer for human breath the combined measurement of CO2 content and particle size distribution can be used to indicate air contamination by germs and particles emitted by humans. Indoors it is thus possible to determine the fraction of the air that has been exhaled by persons present and contains potentially infectious particles. This kind of data evaluation is a new dimension for assessing indoor air quality and is available as an "infection risk indicator" (pat. pending) in the AQ Guard.


Fig. 2: AQ Guard screen view

To achieve better resolution and calculation of aerosol concentration in the particle size range of typical airborne viruses, the resolution of nanoscale particles is increased and lowered to 0.15 µm instead of the usual 0.175 µm.

The resulting improved imaging performance enables a more accurate measurement of particle concentration and concentration progression over time, which is particularly necessary to determine the effectiveness of measures to reduce the particle number concentration.

Extensions / accessories

AQ Guard has fast data interfaces and allows real-time access via Ethernet, Wi-Fi or mobile radio. All measured values are calculated and made available directly on the device. The user thus retains complete control over his data and decides for himself which information is accessible to third parties or should be transmitted. AQ Guard also provides data in various formats (for example as a text file) for later evaluation.

The compact design and the option of power supply via the Ethernet interface (PoE) simplify installation in buildings and integration into existing infrastructure.

AQ Guard is available in two expansion stages:

Basic version

The basic version of AQ Guard provides measured values of the fine dust fraction PM2.5. plus other variables such as temperature, air pressure and relative humidity.

Extension "Indoor Air Hygiene Professional (IAHP)"

Compared to the basic version, the measurement limit for small particles has been extended downwards to 0.15 µm to meet the special requirements for detecting airborne viruses.

The "Indoor Air Hygiene Professional" package is designed to meet the requirements of experts in the field of indoor air and air hygiene and, among other things, additionally determines values of the fine dust fractions PM1, PM4, PM10 including particle size distribution and number concentration of particles.

AQ Control - Software for assessing the air hygiene quality of rooms

The AQ Control software can be used to assess the dispersion and reduction of aerosols in rooms. Up to six AQ Guard systems and an aerosol generator PAG 1000 measure the accumulation, reduction of particle concentrations and PM values over an adjustable period of time and objectively assess measures taken to reduce aerosol and thus also potential virus contamination.

(Software AQControl is part of "Indoor Air Hygiene Professional (IAHP)" package)


  • Technology based on the type approved Fidas® 200 series (EN16450 and MCERTS); simultaneous measurement of CN, PM1, PM2.5, PM4, PM10
  • With "Indoor Air Hygiene Professional" extension: increased counting efficiency for nano-scaled particles from 0.15 µm
  • Computation of air quality index based on measurements of particulates, CO2, and VOC
  • Estimation of infection risk based on measurements of CO2 and particulate matter
  • High accuracy due to advanced algorithms
  • Long term stable due to self calibration for measurement of flow rate, particulates, and gaseous pollutants
  • 2 years operation without calibration
  • Operates on AC, DC, or power-over-Ethernet


Measuring principle Optical light scattering of single particles
Reported data PM1, PM2.5, PM4, PM10, TSP, CN, particle size distribution, ambient pressure, ambient temperature, rel. ambient humidity, CO2, TVOC, Infection Risk Index, Air Quality Index (depending on configuration)
Measurement range (number CN) 0 – 20,000 particles/cm³
Size channels 64 (32/decade)
Measurement range (size) 0.175 – 20 µm (with IAHP-Package installed, starting from 0.150 µm)
Measurement range (mass) 0 – 20,000 µg/m³
Measurement uncertainty R2 > 0.98 for PM2.5 and R2> 0.94 for PM10
versus EN 16450-certified Fidas® 200
(15 min average, each)
Volume flow 1.0 l/min ≙ 0.06 m³/h
Data acquisition Digital, 22 MHz processor, 256 raw data channels
Light source Long term stable LED
Power consumption < 20 W
User interface Touchscreen 800 • 480 pixel, 5" (12.7 cm)
Weight 2.4 kg
Operating system Windows 10 IoT Enterprise
Data logger storage 10 GB
Software PDAnalyze
Response time 1 s, moving average configurable
Aerosol conditioning Optional: thermal with compact IADS
Installation conditions -20 – +50 °C
Interfaces USB, Ethernet (LAN), Wi-Fi, optional: 4G
Protocols UDP, ASCII
Dimensions 175 • 280 • 140 mm (H • W • D)
Linearity 0.95 – 1.05 (measured against EN 16450 certified Fidas® 200)


  • Industry:
    • Production processes
    • Bulk material handling (mixing, discharge, storage, packaging etc.)
    • Fenceline Monitoring
  • Construction sites: Roads, railroads, demolition sites
  • Buildings: Schools, kindergartens, hospitals, hotels, offices, public service buildings
  • Residential buildings near construction sites or other polluted areas
  • Public transportation: Airports, train stations, tramway & underground stations, cruise ships, passenger cabin, e.g. in tram, train


Brief Description
Brief product description in two-pages as PDF
Product Description
Detailed product description as PDF


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