Microbiological contamination is an essential quality parameter in air-conditioned rooms, which has to be thoroughly controlled.

This is especially essential in the hygienically sensitive area of health care facilities as well as in food and drug production facilities.

According to VDI regulation 6022, the facility’s operator is liable to ensure the microbiological cleanliness of the heat, ventilation and air conditioning system (HVAC system) by periodic contact plate sampling of the inner air duct wall. Such contact plate samples have to be incubated for several days and analysed in a qualified microbiological laboratory.

Locally enhanced air humidity and condensation events may facilitate microbial growth and increase the bio burden of the supplied air sporadically as well as permanently. Consequently, such microbial contamination may remain unrecognized between the test intervals for a longer period of time.

Hence, neither periodic sampling with contact plates nor cyclic replacement of filters allows for the continuous real-time control of the hygiene condition of the supplied air. The aim of this research project is to develop a system which permanently and cumulatively monitors micro-organisms at the inner duct wall of air-conditioning systems. It will replace contact plate sampling, ensure continuous real-time monitoring, permit more effective maintenance and filter change intervals, and consequently improve the quality of supply air.

In principle, the development of the test system is based on an ion jelly detector, which resembles contact plates by means of its gelatinous structure but is permanently stable to collect airborne microbial contaminations for extended periods of time.

The ion jelly immobilises micro-organisms on its surface, prevents microbial growth, and includes a fluorophore precursor. The microorganisms’ enzymatic capacities convert the precursor into a fluorescent product which is continuously measured and quantified by the increase of its specific fluorescence.

The readout is either facilitated by distance measurement through an optical window at the opposing wall of the air duct or by direct optical fiber readout in the ion jelly itself. The data acquisition may be achieved manually by periodic readout on a mobile device or permanently by coupling with pre-installed monitoring or measurement systems.

Cleaning and hygiene service providers benefit from the new system as well as hygiene consultants, who are responsible for the hygiene testing of HVAC systems and manufacturers of HVAC systems or filter materials.

Furthermore, such a system will minimize liability risks for about 500,000 operators of HVAC systems in the areas of health care, food, pharmaceutical and cosmetics industry and improve their competitiveness.

The research report is available on request from FRT.