Demand-Controlled Ventilation - Requirements and Control Strategies

Most standards for air handling systems prescribe a minimum air flow rate per person per hour based on full occupancy of the ventilated space. The number of occupants may fluctuate widely, however, and demand-controlled ventilation (DCV) responds to the actual demand for air renewal. There are now sensors capable of detecting this demand, and these are a prerequisite for DCV and good air quality. Key features of DCV are the incorporation of thermal tolerance bands (heating/cooling, humidification/dehumidification), and special control strategies to reduce or even disable the air flow rate.

Sensorial and Instrumental Approaches to Indoor Air Monitoring

The paper deals with a research about analytical techniques for meaningful, reliable, cost-effective, in-situ, real-time and continues determination of airborne chemicals, by means of a new electrochemical sensor; the research aims to develop objective instrumental sensing systems able to substitute the subjective human responses. Sensor detection capability could regard a series of analytes: carbon dioxide, carbon monoxide, inorganic pollutants, ammonia and other metabolic gases, irritants, odours.

Test method for describing directional sensitivity of anemometers for low-velocity measurements indoors.

Thermal anemometers with omnidirectional sensors are recommended in the standards to be used for low-velocity measurements indoors. Requirements for the directional sensitivity of the velocity sensor are prescribed. However, a method for testing the directional sensitivity of low-velocity anemometers does not exist. A simple test procedure is used in practice to identify the so-called "yaw" and "roll" directional sensitivity of an omnidirectional velocity sensor.

Impact of natural convection on the accuracy of low-velocity measurements by thermal anemometers with omnidirectional sensor.

Thermal anemometers with heated velocity sensors are mostly used for low-velocity measurements in rooms. The heated velocity sensor generates an upward, free convection flow that interacts with the airflow where measurements are to be performed and, thus, has an impact on the accuracy of the velocity measurements. Tests were performed with four anemometers available on the market to identify this impact in an airflow with a constant velocity and in an airflow with a periodically fluctuating velocity.

Indoor air quality sensors.

Demand controlled ventilation systems can be used to minimise energy consumption whilst maintaining satisfactory levels of indoor air quality (IAQ). As an alternative to C02 sensors IAQ sensors (based on Taguchi mixed gas sensors) can be used to infer levels of IAQ. This Technical Note provides details of a series of laboratory and site tests to determine the performance of a range of IAQ sensors.

Measured field performance and energy savings of occupancy sensors: three case studies.

Occupancy sensors have the potential to significantly reduce energy use by switching off electrical loads when a normally occupied area is vacated. While occupancy sensors can be used to control a variety of load types, their most popular use has been to control lighting in commercial buildings. Manufacturers claim savings of 15% to 85%, although there is little published research to support the magnitude or timing of reductions.

Chemical indoor air quality control.

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