Duct Air Quality (VOC) Transmitter QDT 24

The duct air quality (VOC) transmitter QDT 24 provides reliable solutions for energy management through Demand Control of Ventilation (DCV) systems in buildings.

The self-calibrating microprocessor-controlled duct air quality transmitter QDT 24 is used to determine the air quality on basis of a mixed gas sensor / VOC sensor
(VOC = volatile organic compounds).

Duct Air Quality transmitter QDT 24 is used for:

- Air quality measurement in offices, hotels, meeting rooms and convention centres, apartments, stores, and restaurants, etc.

- Quantitative evaluation of room air pollution with contaminating gases such cigarette smoke, body perspiration, exhaled breathing air, solvent vapours, emissions from building members and cleaning agents.

- Adjustable sensitivity regarding the maximum air contamination to be expected.

- For room ventilation as-needed, enabled by air changes only taking place when air is polluted while conserving energy at the same time.


Room air quality is understood as subjective air quality, felt by human beings with their olfactory organs.

As perception varies from person to person and therefore, air quality is assessed differently, a general definition of criteria for room air quality is not possible.

By linearising and high operating temperatures, the air quality sensor achieves marginal drift and good stability.

The sensor is automatically self-calibrating.

The air quality sensor does not trace the concentrations of individual gases,
but assesses the mixed gas as such, i.e. gas concentrations are not measured selectively.

Therefore, it is not possible to specify gas concentrations by the unit ppm.

Detectable gases: mixed gas, vapours of alcanoles, cigarette smoke, automobile exhaust gases, exhaled breathing air, combustion smoke (from wood, paper, plastics).

In addition, compounds of alkanes, alkenes, aromats, terpenes, halogenated hydrocarbons, esters, aldehydes and ketones as well as native VOCs such as terpenes and isoprene are ranking among volatile organic compounds VOC.

VOCs also evaporate from chemical products used in construction such as coating compounds, adhesives, or sealing compounds, furnishing objects, cleaning and care products, office chemicals and floor carpeting.

The sensor’s service life is depending on the type of burden and gas concentration and is more than 60 months under normal load conditions.

The new design implies the alternative to choose between three sensibility ranges by means of DIP switches, comparable to three measuring ranges: LOW for low, MEDIUM (default, equivalent to the hitherto existing type of this device) for medium, and HIGH for high noxious gas contaminations.

Technical data

VOC sensor (metal oxide) with automatic self-calibration

Sensor protection
sinter filter, exchangeable, screwed, easy to clean

Measuring range
0-100% air quality referred to calibration gas multi-range switching
(selectable DIP switches) VOC: LOW - MEDIUM - HIGH

Measuring accuracy
+/- 20% EW of final value (referred to calibration gas)

Power supply
24 Vac/dc

0-10 Vdc or 4-20 mA (selectable)
and potential-free changeover contact
(24V)switch point adjustable from 0-100% of the output signal.

Ambient temp.range
-10 to +60°C

Warm-up period
1 hour

Response time
< 10 s. minimum flow rate 0.2-0.5 m/s

Plastic, material polyamide 30%
glass-globe-reinforced with quick-locking screws,
72 x 64 x 37.4 mm
Cable gland M 16 x 1.5, incl. strain relief, max inner dia. 10.4 mm

Probe tube
Poliamide (PA6) dia 20 mm, lenght 202.5 mm,
with torsion protection

Process connection
by mounting plastic flange (including in the scoope of delivery)

Protection type
IP 65 (according to EN 60529)enclosure only

Protection class
III (according to EN 60730)

electromagnetic compatibility according to EN 61326,
EMC directive 2004/108/EC

Download datasheet

Duct Air Quality (VOC) transmitter QDT 24.pdf

Download CE declaration of conformity

CE declaration of conformity Air Quality (VOC) transmitter QDT.pdf

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