## 4 Personal Climatization Systems  
Personal climatization systems individually improve the indoor climate within the operation range of the occupant and are highly suitable for open-plan offices or vehicles. Effective heating in cold environments is mainly achievable by using heated surfaces, radiant heaters and warm air. Personal cooling is especially done by applying directed air flow. The cooling effect can be further improved by preconditioning the air down to a lower air temperature. Personal ventilation is the supply of fresh, preconditioned air towards the breathing area of the occupants and improves the quality of the inhaled air, which improves thermal comfort and perceived air quality. Simultaneously, the concentration of the contaminants in the inhaled air is reduced and therefore, the risk of cross-contamination is lowered. Personal climatization individually improves the local thermal environment under consideration of individual thermal preferences and hence, reduces complaints about the indoor climate. Thermal optimization of the workplace leads to a higher productivity and improved health of the staff [6, 30]. Higher quality of the inhaled air reduces the amount of absence days, which further improves the productivity of the occupants. Although several studies have shown that occupants request for a higher air velocity especially in a neutral to warm environment [67, 68, 69, 70, 71], current standards generally restrict the use of air velocity for air-conditioning [9, 18]. The energy-efficient implementation of personal climatization must be accompanied by the application of an extended target temperature range of the HVAC system. However, the possible, optimal energy-efficient ambient temperature range depends on the building size, outdoor climate, occupancy and must consider the thermal comfort of the occupants within the building [72]. Personal evaporative coolers with supply of 100% fresh air reduce the cooling energy demand by 6% K\({}^{-1}\) due to the related possible increase of the maximum room temperature [73]. The cooling energy savings can be enlarged to 25% K\({}^{-1}\) by supplying 40% recirculated room air. Using personal fresh air supply, the influencing factors on the energy demand of the HVAC system differ between cold and hot humid outdoor climate [74, 75]. According to [PERSON] et al. [74], in hot and humid regions such as Singapore, the introduction of personal fresh air supply can save up to 51% of the energy compared to mixing ventilation. Their calculation is based on the assumption that the maximum room air temperature increases from 24 \({}^{\circ}\)C to 28 \({}^{\circ}\)C, the volume air flow decreases from 6.5 L s\({}^{-1}\) to 2.5 L s\({}^{-1}\) and the personal thermal actuators are solely enabled when the occupant is present. As revealed by [PERSON] and [PERSON] [75], in high standard heat insulated buildings of cold regions such as Copenhagen, the use of personal climatization systems saves up to 60% of the energy consumption of the HVAC compared to mixing ventilation. To achieve this, the supply temperature must be preconditioned to a low, but thermally acceptable temperature. In addition, the maximum indoor temperature must be guaranteed to be thermally acceptable. The latter is of highest importance for saving energy, because otherwise the energy consumption would be higher than without personal climatization systems since, as a result of the essential heating of the supply air for thermal acceptance, the cooling load would be extended, too. [PERSON] et al. [29] evaluated a personal environmental control system, consisting of preconditioned supply air on top of the desk, a radiant heating panel below the desk and individual lighting control implemented in office buildings of a bank in San Francisco. The accomplished system reduces the dissatisfaction with the thermal quality and air quality to 0% and 6%, respectively. Both, thermal quality and perceived air quality, increase by 0.84 scalesteps and 0.46 scalepoints (bipolar seven point scale), respectively.