Mixing and displacement ventilation compared in classrooms; distribution of particles, cat allergen and CO2

Mixing ventilation and displacement ventilation were compared in an intervention study inclassrooms. Particles, cat allergen and CO2, were measured in classroom air at different levelsabove the floor, during regular lessons. With mixing ventilation, the particle concentrationtended to decrease with height, with a stronger gradient occurring for larger particles. Withdisplacement ventilation, the particle concentration increased with height, except for particles>25 m. The displacement system thus tended to have a slight upward displacement effect onmost of the particles.

A study of demand-controlled ventilation (DCV) and constant air volume (CAV) systems

One of the most common measures of IAQ (indoor air quality) is carbon dioxide, CO2, generated by human respiration, in particular, where the main source of pollutions are occupants. In this report, the occupancy-related pollutants are considered as the main pollutant source. However, other type of sources may also be removed satisfactory when governing the ventilation system for removal of

Simulations of indoor air quality and ventilation impacts of demand controlled ventilation in commercial and institutional buildings

Carbon-dioxide (CO2) based demand controlled ventilation (DCV) offers the potential for moreenergy efficient building ventilation compared with constant ventilation rates based on designoccupancy. A number of questions related to CO2 DCV exist regarding energy benefits, optimalcontrol strategies, and indoor air quality impacts for contaminants with source strengths that areindependent of the number of occupants. In order to obtain insight into these issues, a simulationstudy was performed in six commercial and institutional building spaces.

Demand control ventilation systems : performances of CO2 detection

In France, in non residential buildings, these systems are generally controlled by either a CO2 sensor or optical movement detection (infrared).The part of the study we present here was to determine :- laboratory tests methods to assess the performances of CO2 sensors for ventilation application.- the working performances of these sensors, and particularly the long term stability in a meeting room.- a methodology to assess the performances of CO2 DCV system in French technical agreementThe main results of this study are :- it is easy to characterize (to calibrate) the sensors- the long term

Increased levels of bacterial markers and CO2 in occupied schools

The aim of this study was to test the following hypthesis : in schools, bacterial markers may be increased in indoor air because of the presence of children.Dust samples were collected from the school rooms when occupied but also when unoccupied during the week-end. Results have been analysed and the conclusion is that in unoccupied rooms the airborne dust is of environmental origin, whereas the increase level of dust in occupied rooms is due to the children presence.

Dynamic evaluation of airflow rates for a variable air volume system serving an open-plan office

This paper proposes a space zone model for the calculation of all the airflow parameters based on tracer gas measurements, including flow rates of outdoor air, VAV supply. This approach gives a practical protocol for buildings managers to evaluate the performance of airside systems and determine air-conditioning and ventilation system performance parameters within acceptable errors.

Risk of indoor airborne infection transmission estimated from carbon dioxide concentration

Accurate mathematical models of airborne infection are needed to estimate the risk from secondary transmission of biological warfare agents. An equation has been derived by the authors : they determined the fraction of inhaled air that has been exhaled previously by someone in the building by using a CO2 concentration as a marker for exhaled-breath exposure.
There is a critical rebreathed fraction of indoor air below which airborne propagation of common respiratory infections and influenza will not occur.

Carbon Dioxide Levels and Summertime Ventilation Rates in UK Schools

Measurements of metabolic carbon dioxide concentration made in four classrooms in two schools are reported for both occupied and unoccupied periods. Measurements were taken for approximately one week in each classroom during the unheated season and the time-varying ventilation rates estimated. The results of the experiments show CO2 concentrations that are far beyond the guideline value of 1000 ppm (the maximum concentration during the occupied period was 3756 ppm). Calculated air supply rates vary from unacceptably low levels, to rates that are in line with guidance.

Carbon Dioxide Levels and Ventilation Rates in Schools

In the following, measurements of CO2 levels in seven classrooms in four schools are reported. Measurements were taken for approximately one week in each classroom during the heating season and the time-varying ventilation rates estimated. The results of the experiments show CO2 concentrations which are far beyond the guideline value of 1000 ppm (the average concentration during the occupied period was 1957 ppm). In some classrooms the level exceeded the range of the detector (4000ppm).

Energy labelling of existing buildings and their equipment: new procedures to assess possiblities for increasing energy efficiency while reducing CO2 emission and improving comfort.

Describes best practice for energy labelling for existing residential buildings in four countries. Also describes the specific features of a Belgian procedure for on-site evaluation of both equipment and building envelope. The results can be used by other countries as general guidelines to develop or optimise efficient and effective energy labelling procedures.