**4. Use of microbiological measurements for numerical model implementation and validation**

Microbiological measurements of particle concentration were used to assess particle emission rates imposed as boundary conditions in the numerical models. Particle emission rate per person, distinguished for dimension, was not known a priori during our research. Zhao et al. [29] considered a constant generation rate of 0.0916 µg/s per person for each particle size group. For each particle dimension, referring to an assumed particle density of 1.05E-6 µg/µm3 , scaling the emission rate by the particle volume, it is possible to obtain the related number of particles emitted by a person in the time unit. Quian et al. [30] used a different method to assess particle emission rate, divided for different diameters, caused by the occupants in a classroom. They experimentally measured the particulate concentration at specific locations in the classroom for similar environmental conditions, but with and without people presence. They argued that difference in acquisitions could be attributed to emissions due to occupant contribution, and then proposed a particulate emission distribution as a function of particle diameter. The emission rate refers to how many particles of a specific dimension are supplied by one person in the time unit to the surrounding environment. The two above mentioned approaches provide different results. In our investigation, we evaluated particle emission due to each occupant, differentiated for diameter dimension, using the experimental acquisitions of particle concentration in the real OT with and without patient and medical staff presence. In particular, we applied a similar method used in [30] to assess the particle emission rate by occupants to be used in the numerical models. Otherwise, in our case we combined the available experimental data with results coming out from numerical simulations to assess the emission rate of particles per person depending on particle dimension. The procedure used is given in the flow-chart diagram of Figure 5: the caption "sampling points" refers to points PT01, PT02, PT04 and PT05, "particle diameter range" means (0.3-0.5 µm); (0.5-1 µm); (1-5 µm), and "average particle diameter" refers to the average values of the particle diameter (0.4; 0.75; 3 µm) computed for each of the previous ranges.

presence and movements that produce local temperature and airflow modifications. The air

**Figure 4.** Comparison between numerical results (NUM, black grey) and mean-average experimental data (EXP, light grey). Error bars indicate the detected experimental deviation (minimum and maximum value). Circled and squared symbols (referring to the second y-axis) indicate the maximum deviation of numerical values from experimental data, and deviation of numerical results from experimental time averaged data, respectively. Temperature (a), RH (b) and

Microbiological measurements of particle concentration were used to assess particle emission rates imposed as boundary conditions in the numerical models. Particle emission rate per person, distinguished for dimension, was not known a priori during our research. Zhao et al. [29] considered a constant generation rate of 0.0916 µg/s per person for each particle size group.

the emission rate by the particle volume, it is possible to obtain the related number of particles emitted by a person in the time unit. Quian et al. [30] used a different method to assess particle emission rate, divided for different diameters, caused by the occupants in a classroom. They experimentally measured the particulate concentration at specific locations in the classroom for similar environmental conditions, but with and without people presence. They argued that

, scaling

For each particle dimension, referring to an assumed particle density of 1.05E-6 µg/µm3

velocity (c) values are reported at locations PT01, PT02 and PT03 (as shown in Figure 1).

**implementation and validation**

526 Current Air Quality Issues

**4. Use of microbiological measurements for numerical model**

velocity values globally fit the standard limits, suggested for unidirectional flow.

**Figure 5.** Flowchart of method used for estimating the occupant particle emission rate per diameter by an iterative cross-comparison between numerical and experimental data.

Comparison between experimental and numerical (NUM) particle concentration due to occupants in the OT is shown in Figure 6. In this figure, experimental value (EXP) for each diameter (di ) represents the difference between average data (Av) acquired for the at rest (rest) and operational (oper) conditions, computed as follows:

$$EXP\_{d\_i} = A\nu \left(EXP\_{d\_i}\right)\_{oper} - A\nu \left(EXP\_{d\_i}\right)\_{rest} \tag{3}$$

while the error bars are plotted by assuming the following:

$$Err\_{d\_i}^+ = \max\left\{EXP\_{d\_i}\right\}\_{oper} - \min\left\{EXP\_{d\_i}\right\}\_{rest} \tag{4}$$

$$Err\_{d\_i}^- = \min\left\{EXP\_{d\_i}\right\}\_{open} - \max\left\{EXP\_{d\_i}\right\}\_{ret} \tag{5}$$

Numerical values plotted, refer to the "final" particle emission rate per average diameter applied to the exposed person surfaces carried out from application of the computing proce‐ dure shown in Figure 5. Values of emission rate for diameter range are provided in Table 5, where values suggested in the previous literature are also reported.

**Figure 6.** Particles concentration per diameter in different locations: comparison between experimental and numerical values.

Despite an iterative application of our proposed "guess and check" procedure, experimental/ numerical difference in particle concentration at point PT01 remained quite high: the numerical model overestimates particle contents in the air at this location. Otherwise, a good agreement can be pointed out from comparison of particle concentration at the other different locations. Obtained results of particle emission rate per diameter and per person (Table 5), provide lower values with respect to those proposed by Quian et al. However, this is an expected result,


**Table 5.** Particle emission rate (particles/s) from persons differentiated by diameter.

because measurements by Quian [30] refer to a different indoor environment (university classroom) with different use conditions, occupied by students.
