## 3 Results
### Question 4: How to Collect Data
#### 3.4.4 Laboratory Experiments  
Laboratory experiments were also applied in the various studies on IEQ evaluation models. Compared with field studies, environmental quality could be controlled in laboratory experiments, which is both advantageous and disadvantageous. In the experiment chambers, more combinations of the various environmental settings can be tested, and researchers could effectively collect the occupants' responses toward different conditions. However, it is hardly possible to control every IEQ indicator in the experiment chamber, so previous studies conducted in the labs seldom considered all the aspects of IEQ. For example, in the study by [PERSON] et al. [58], only thermal, visual, and space conditions could be changed; therefore, acoustic quality and IAQ were not examined. In the study by [PERSON] et al. [57], lighting, acoustic, and thermal conditions could be controlled, while IAQ could not; therefore, their IEQ evaluation did not consider IAQ. Another possible limitation of the laboratory experiments is the limited size of the experience chamber and the limited number of participants. [PERSON] et al. [82] experimented in an IEQ laboratory where all the IEQ aspects (including temperature, airspeed, SPL, illuminance, and CO\({}_{2}\) concentration) could be changed, yet only eight university students participated in their experiment, which made it impossible for the results to be generalized. Besides, in this experiment, IAQ was controlled by increasing the CO\({}_{2}\) concentration, which was irrelevant because CO\({}_{2}\) concentration cannot be regarded directly as an indicator of IAQ. CO\({}_{2}\) concentration, without specific intervention, can affect the ventilation performance, which could be used to evaluate the IAQ; however, increasing CO\({}_{2}\) concentration by releasing CO\({}_{2}\) into the chamber can hardly have any connection with the ventilation rate, hence, there is no impact on IAQ. Although there are several limitations to the current laboratory experiments, with technological progress, there is reason to believe that more advanced experimental chambers will be designed and built. Laboratory experiments will provide a powerful way to study IEQ models in the future.  
No unified data collection methods have been developed, including both subjective and objective investigations. The empirical data collection procedures varied from study to study, which increased the uncertainty in the collected data and affected the trustworthiness and credibility of the IEQ models. Therefore, one of the most basic needs when establishing an accurate IEQ model is to define a standard, detailed, and widely applicable protocol for data collection. A standard questionnaire (for capable adults) and interview outline (for young children and older adults) including all the basic questions should be provided for subjective investigation. On this basis, several customized questions for the different indoor environments can be added, and many examples should be included in the protocol, while in the case of objective investigations, the procedures of on-site measurements (for existing buildings) and simulations (for future buildings) should be introduced in detail. In addition, the customization of objective investigations is also feasible, and possible options should be provided, based on previous studies. Following this protocol, a global database can be developed that will pave the way for establishing universal IEQ models.