## 3 Results and Discussions
#### 3.3.1 The Temporal Characteristics  
Considering that there existed apparent cyclic patterns on the four environmental parameters recorded by indoor nodes in three consecutive days, for display purposes, the following Figure 12 solely plotted the latest associated 24-h data that ranged from 13 August to 14 August. During most of the whole day no apparent distinctions existed among all the indoor nodes distributed over six different sites, except for nodes of Column A and Column B that reported about 1.5 \({}^{\circ}\)C lower temperature than others in the night and early morning. In addition, all indoor nodes reached a consensus of approximating the highest temperatures (ranged from 25 to 26 \({}^{\circ}\)C) in around 15:00. Contrarily, the relative humidity displayed inverse diurnal variation patterns compared with that of temperature variation. Nodes mounted on Column A and Column B, which had the lowest temperature, instead reported the highest relative humidity during the whole-time span. According to the national standard of People's Republic of China of environmental parameters for intensive pig farms namely GB/T 17824.3-2008 [33], the ambient temperature and relative humidity of commercial barns for gestating sows should be maintained between 15 and 20 \({}^{\circ}\)C, and from 60% to 70%, respectively. Meanwhile, the recommended lower critical temperature (LCT) and upper critical temperature (UCT) are 13 and 27 \({}^{\circ}\)C. Although there exhibited a daytime high temperature (above 24 \({}^{\circ}\)C) starting from 10:00 to 16:00, however, it is yet acceptable in the thermoneutral zone and thereby beneficial to the welfare of gestating sows in this mechanically ventilated commercial pig house during the summer. As for the relative humidity limits, it is recommended to operate them in the barns of gestating sows from 50% up to 85%. Figure 13 nevertheless indicated that nodes from Column A and Column B reported substantial records of rather high relative humidity (over 85%) that occupied 13% and 63% of the two consecutive days' entire observations. Generally speaking, the higher the humidity level in the air, the less effective is the process of evaporative heat loss to help the sow cool off [31]. Thus, the sow would feel the effects of heat stress regardless of the relatively moderate temperature, which might cause high body temperature, affect the sow's metabolism, reduce feed conversion rate and daily weight gain, etc. Considering that nodes mounted on Column B that reported high relative humidity for most of the time (63%) were 150 cm above the ground located overhead of the sow, thereby, they could only reflect the ambient air humid condition. In terms of nodes from Column A which were 60 cm above the ground located in the respiration zone of the sow, they were capable of approaching to the realistic relative humidity that the sow could feel. They spotted high relative humidity around 08:00, 14:00, and 16:00 on the first day, and the period from 08:00 to 11:00 on the other day. Despite of the fact that monitoring the relative humidity for a much longer period of time is indispensable to uncover the underlying variation pattern of relative humidity in this swine confinement building, those periods above can still somehow provide practical guidance values to maintain the relative humidity level in a comfortable zone for the gestating sows, for instance, by appropriately increasing the ventilation rate. The GB/T 17824.3-2008 standard required that the indoor CO\({}_{2}\) concentration should not exceed 1500 mg/m\({}^{3}\), while [PERSON] [34] recommended that a good target for the CO\({}_{2}\) levels in a pig house was less than 2700 mg/m\({}^{3}\). Although the CO\({}_{2}\) concentration inside this commercial pig house had been above 1500 mg/m\({}^{3}\) for the whole time, there merely existed two time periods when the CO\({}_{2}\) levels exceeded the 2700 mg/m\({}^{3}\), namely: ranging from 07:00 to 08:00 and from 14:00 to 15:00.