Field measurement of indoor environment of underground garage in winter and analysis of its influence on people

. Since the National Fitness has become a national strategy, people’s enthusiasm for fitness has also been increasing. When winter comes, the outdoor temperature becomes unsuitable for people to carry out exercise activities. Therefore, more community residents choose underground garages as a place for fitness activities. Due to the frequently entry and exit of vehicles and ventilation restrictions in the underground garage, whether the internal air quality in an underground garage meets the requirements of personnel activities remains to be studied. In this study, an underground garage in a residential area of Jinan was tested. The parameters involved CO 2 , CO, PM2.5, temperature and relative humidity. Select areas where people often gather for measurement. According to the test results, the distribution of CO 2 , CO, PM2.5, temperature and relative humidity in the underground garage were quantitatively analyzed. It is found that the air quality in some areas of the underground garage is poor, and long-term activities in this environment will affect people's health. To solve this problem, in this study, the area with relatively good air quality in the underground garage is found to provide personnel activities, and the optimization measu.res of winter ventilation in the underground garage were put forward.


Research Subjects
This study mainly selects the underground parking garage of a residential district in Jinan for testing, which is located in the first underground floor of the residential building, an area of about 7700 m 2 . 266 parking spaces in the garage. Through the preliminary survey found that the concentration of vehicle access time is between 7:00 ~ 8:00 in the morning and 6:00 ~ 8:00 in the afternoon.
The garage uses a combination of natural ventilation and mechanical ventilation, and the number of air changes is 6 times per hour.

Test items and test time
The inhalation of CO in human body can cause hypoxia, which can cause dizziness and weakness in mild cases, and even death in severe cases [5][6][7]. Temperature, relative humidity and CO2 are an important indicator of air quality [9][10]. PM2.5 particles are small in size, rich in a large number of toxic and harmful substances, thus having a greater impact on human health and atmospheric environmental quality [11]. In summary, the measurement parameters selected for this test were CO concentration, CO2 concentration, air temperature and relative humidity, and PM2.5 concentration.
The test time was arranged in the evening from 19:30 to 21:00, through the preliminary survey, this time belongs to people's rest time after dinner, and more residents choose to enter the underground garage activities during this time.

Measurement instruments and test methods
The instruments used for the measurements included the TSI8530 benchtop dust meter and Tsi7575 indoor air quality detector. Tsi8530 was used to measure PM2.5 in the air. Tsi7575 for measuring CO, CO2, temperature and relative humidity. All the above equipment has been calibrated and verified by metrology and qualified to meet the requirements for use as specified in the testing specifications.
Since the number of cars in the garage varies every day, and the content of various components of the air in the garage also varies, if each measurement point is measured only once, the data will produce large inaccuracies. So that each point in the garage is measured continuously for seven days, and finally the measurement data of the seven days are averaged. The measurement point arrangement is shown in Fig. 2 below. Thirty minutes after the test started, the concentration of PM2.5 gradually stabilized, and its fluctuation range was between 50~60 μg/m 3 . It can be seen in Fig. 4 that the PM2.5 changes in a small range and is in a stable state.     the test period, which shows that the relative humidity of all four points is below 30%, and the relative humidity of points 1, 2 and 3 varies between 20% and 25% most of the time. The relative humidity of point 4 is higher than the other three points, and its fluctuation range is 25% to 30%.
The relative humidity of the four measurement points is in a relatively stable state although there are variations. prone to infection and respiratory diseases such as colds [13][14].
In summary, the place of winter personnel fitness activities can be chosen in the underground garage, although attention should be paid to the operation of vehicles and the timing of activities, and the air environment in the underground garage to meet the safety standards of personnel activities.

Conclusion
1) In this study, the air quality in the underground garage was measured to analyse whether people could perform short-term fitness activities in the underground garage in winter.
2) The difference between the air environment of garage entrance and garage interior is obvious, because the garage entrance is the same as the outside environment, it is more influenced by the outside environment. Therefore, it is not suitable for personnel activities near the garage entrance and exit, and the difference between the air environment in the aisle inside the garage and the corner area of the loadbearing column of the garage is small, and personnel activities should be selected as close to the internal location as possible. Personnel activities need to pay attention to always ensure their own safety, as well as control the time of activities, cannot use the underground garage as a long-term activity place.