# System for Indoor Comfort and Health Monitoring Tested in Office Building Environment
## 2 Indoor Comfort  
The concept of comfort refers to a specific condition of well-being [29] based on the indoor environment perception through the occupants' senses [29] and comprises all of the parameters monitored and controlled through installations, which directly influence peoples' moods and act on their senses, such as thermal, acoustic, olfactory and visual comfort [30]. Indoor environmental quality (IEQ) can positively or negatively influence occupants' health. Thus, IEQ includes a series of factors, four of which are considered of maximum importance. These directly influence the perception of the indoor environment and, at the same time, can also have an effect on the physical and mental states of users [27; 30]. The main factors regard thermal comfort or the indoor climate, which is mainly based on temperature and humidity, air movement/speed and temperature; visual comfort or the quality of lighting, determined by the visual field, the illumination level, reflection and other parameters; indoor air quality, which is a complex factor that includes odours, indoor air pollution and the maintenance of clean air; and acoustic quality, influenced by indoor/outdoor noise and vibrations [31; 32]. Thermal comfort is defined by ASHRAE in the ANSI/ASHRAE 55-2013 standard [33], but also by ISO 7730:2005 [34], as that state of mind that expresses satisfaction in relation to the surrounding environment. These standards propose thermal comfort equations only for naturally ventilated buildings, which are not conditioned. Adaptive thermal comfort is quantified by comfort equations established by specific data from certain climates. According to Romanian legislation, the I5 standard [35] is used for the design of ventilation installations, which are based on the comfort categories provided by EN 15251:2007 (currently withdrawn) and are referred to as ambiance categories. Regarding adaptive thermal comfort, the standards are more restrictive, and the design and evaluation of buildings according to this method are only allowed by ISO 7730 and ASHRAE 55 standards. A study performed by the World Green Building Council [36] led to the following conclusions and recommended values:  
* _Indoor air quality_: The improvement in occupants' health and productivity in office buildings as a result of increased indoor air quality is well known. Increased CO\({}_{2}\) concentrations, pollutants and low ventilation rates affect these buildings. The main findings of the conducted study revealed an improvement of 8 to 11% in productivity provided by increased air quality. Thus, when analysing the indoor CO\({}_{2}\) concentration values shown in Table 1, it can be noticed that they increase when the building is occupied and there is no ventilation. At the end of the day, in a classroom without natural or mechanical ventilation, CO\({}_{2}\) concentrations can reach values of up to 4000-5000 ppm [37]. An improvement in air quality can be achieved by mechanical ventilation by exhausting the used indoor air and introducing fresh outdoor air. This air movement is performed by using fans [37]. The role of ventilation inside buildings is mainly to maintain increased air quality by diluting pollutants. Specifically, the steady-state concentration of a pollutant at a given emission rate is dependent on the ventilation rates. As the ventilation rate increases, the final steady-state pollutant concentration decreases [38]. The fundamental goal of the smart ventilation concept is to reduce the consumption and cost of ventilation energy while maintaining at least the same level of air quality compared to a continuously operating ventilation system [39]. Humidity values, as shown in Table 2, play an important role in the thermal comfort state. For example, high humidity accentuates the heat sensation in the summertime, while low humidity in the wintertime causes discomfort related to the respiratory system. During the winter season, generally, the outdoor humidity is lower, which is also reflected indoors [37].