Type and Density of Bacterial and Fungal Bioaerosols and Particles in Inside and Outside of Hospital: Modeling of Dispersion and Antibiotic Resistance of Bacterial Bioaerosols

The study of loading rate of microorganisms in the space of hospital inside and outside to evaluate their impacts on physical health of patients and staff, as well as to nd out the source of possible infections and allergies stemming from the presence of bioaerosols is of great importance. In total, 262 bacterial and fungal samples were collected from the air of the wards of Tohid Hospital, Sanandaj, Iran. Also, suspended particles were measured by Particle Mass Counter (model: TES-5200). Parameter such as relative humidity and temperature were recorded by using TES-5200 device. To identify bacteria, some biochemical and molecular tests were conducted. And, for the identication of fungi, microscopic and macroscopic characteristics were used. The highest and lowest densities of the bioaerosols were observed in lung and operating wards (336.67 and 15.25 CFU/m 3 ). Moreover, the highest and least concentrations of particles were seen in the emergency and operating wards, respectively. The most common fungi isolated from the hospital air were Penicillium (24.7%), Cladosporium (23. 4%), Aspergillus niger (13.3%) and Aspergillus Flavus (11.4%). Furthermore, the highest concentration of the isolated bacterium was Staphylococcus hemolyticus (31.84%). And, the bacteria had the most resistance to antibiotic gentamicin.The general average of air pollution of the hospital to bioaerosols in quantitative terms was higher than that suggested by international organizations. Considering the high concentration of bioaerosols and particles in the hospital studied, provision of optimal conditions (like temperature, humidity, suitable ventilation and intelligent air conditioning system) and imposing a restriction in the entrance of the wards can be utilized to reduce the amount of pollution.


Introduction
Suspended particles contain biological and non-biological substances that can be transported by air ow (Sepahvand et al. 2016). Bioaerosols are de ned as aerosols or any other gas containing a living component or particles released from a living organism. The size of bioaerosols varies from 0.1 µ to about 100 µ. In a general classi cation based on the nature of bioaerosols, they can be divided into the following three categories: a) viruses and parasites b) living organisms including: bacteria and fungi c) parts of microorganisms or products derived from them such as spores, plant pollen, endotoxins and animal allergens (Zare sakhoydi 1395).
Fungi and bacteria constitute a large range of microorganisms in a hospital environment. Level and variety of biological pollution in the hospital environment depend on various factors such as the number and activities of visitors, patients, design of hospital rooms, disinfection methods, dust in the air and so forth (Saadoun et al. 2008). Today, the transmission of viruses and pathogenic bacteria is recognized as an important route for a wide range of nosocomial infections. According to studies estimations, 10% of nosocomial infections are airborne infections and 16% of intensive care unit (ICU) infections are due to airborne pathogen transmission (Mirhoseini et al. 2016). Some recent studies have shown that up to 10-20% of all endemic nosocomial infections may be transmitted through airborne infections. Also, 11% of all deaths in low-income countries are due to lower respiratory tract infection for indoor air pollution (Gizaw et al. 2016). Hospital buildings, as dynamic environments, may be affected by season, weather conditions, design and operation of indoor ventilation systems, moisture penetration, microbial load in the open air, and the number of residents, visitors, and human activities (Verde et al. 2015). In this case, hospital environments require special attention to ensure the health of indoor air quality (IAQ) to protect patients and healthcare staff against nosocomial infections and occupational diseases (El-Sharkawy &Noweir 2014).
In hospitals, Staphylococcus aureus and Streptococcus pyogenes are a global public health problem. These two species are common pathogens in hospitals that may cause severe invasive infections (Gizaw et al. 2016). Park et al. who assessed the levels of of Airborne Bacteria, Gram-Negative Bacteria, and Fungi in Hospital Lobbies, stated that all the lobbies were infected (Park et al. 2013).
Antibiotic resistance is a major problem in the treatment and control of infections. Extensive use of antibiotics in recent years has made some bacteria resistant to broad-spectrum antibiotics from different groups; at present, the presence of multidrug-resistant strains of antibiotics (MDR) is the main problem in the treatment of bacteria such as Pseudomonas aeruginosa in important hospital wards such as burns and intensive care (Adabi et al. 2015). Due to the necessity of antibiotic resistance and its consequences on human health, the resistance of 11 types of bacteria isolated from indoor air to the antibiotics amoxicillin, ce xime, cipro oxacin, azithromycin, gentamicin, doxycycline and sulfamethoxazole were evaluated in this study.
As the rate of nosocomial infections is directly related to the density and type of bioaerosols, thus, determining the type and density of these microorganisms is of particular importance (Massoudinejad et al. 2014). The amount of airborne microorganisms inside the hospital in this study was performed in the internal wards of men and women, infectious, lung, neurology, emergency, ICU, operating room, burns as well as air outside the hospital. Since suspended particles are carriers of biological agents like bacteria and fungi, quantitative analysis of them (PM1, PM2.5, PM4, PM7, PM10) and their relationship with microbial density is of great importance (Cao et al. 2014). Therefore, suspended particle matters were also performed. The modeling of the dispersion of bio-aerosols in different wards and identi cation of bacterial isolates by the PCR method were also determined.

Study area
The Sanandaj composting plant is located at a distance of 8 km from Sanandaj, Iran. Figure 1 shows the geographical location of the biocomposting plant and its units. This plant receives municipal wastes collected from residential areas of the city. The waste is mainly composed of food waste, paper, wood, street wastes, ferrous and non-ferrous metals, glasses, bottles, plastics, etc.

Sampling method
In this study, samples were selected from a number of wards inside the hospital (men's ward, women's ward, lung, neurology, infectious, ICU, burns, operating room, emergency) and the air outside the hospital to determine the quantity and type of bacterial and fungal contaminants as well as particles. The sampling was performed in such a way that all wards of the studied hospital were covered. Sampling in this study was performed in four times in autumn and winter. Inside the hospital, three stations were considered in each ward and in the air outside the hospital, three stations were considered, which sampling was done for four times in each station. In order to evaluate and determine microbial airborne contaminants in the air of different wards, a sampling device (Quick Take-30, SKC, USA) was used. The sampling method with this device is through impact. This device consists of a biostage having 400 holes and a plate containing the culture medium is placed in it. The ow rate of the sampling pump was 28.3 L/min and the duration of sampling air inside and outside the hospital was selected using trial and error at different times for the ow rate to increase the accuracy of the results.
Finally, the sampling time was 20 and 5 min for bacteria and fungi, respectively. For sampling, the sampling device was located at a height of 1.5 m above the ground and at a distance of more than 1 m from the walls and obstacles (Nunes et al. 2005).
Regarding the samples taken from the hospital grounds, these samples were taken from a distance of at least 50 m from the streets.
Before sampling, all devices were rst washed in disinfectant solution (70% alcohol) and then autoclaved for 30 min at standard temperature and pressure. Next, all items were transported in sterile packages to the hospital. In the hospital and in the ward, the prepared sampling series of the device cap with an alcohol pad was sterilized and the sampling was performed. The culture medium used in this study contained bacterial agents: tryptic soy agar (TSA) and fungi: malt extract agar (MEA) containing the antibiotic chloramphenicol.
Particles and dust were measured by Particle Mass Counter (model: TES-5200). This device has the ability to measure particles in two modes: count mode to measure the number of particles in the sizes of 0.5, 0.7, 1, 2.5, 4, 5, 7 and 10 µm and mass mode to measure the volume density level in accordance with the standards PM1, PM2.5, PM4, PM7, PM10. At the same time, the measured volume or ow shows the sample air temperature in terms of °C or °F (10-40°C) and the relative humidity (20-20%) of the sample air. The ow rate is 2.83 L/min or 0.1 CF/min. In other words, the sampling time is 1 min.

Bacterial identi cation
The collected samples were transferred to an incubator (35-37°C). After 40 to 56 h (average 48 h), the culture medium containing the bacteria was examined, and the colonies formed on them were counted. In order to count the colonies, ocular and colony counter methods were used. For bacteriological examination, the cultured samples were taken out of the incubator and all the plates were tested for colony growth, morphology, color and appearance. For microscopic examination of bacteria as well as morphologically (cocci or bacilli) some biochemical tests such as gram staining, catalase, oxidase, urease, OF and IMViC were performed.

Evaluation of antibiotic-resistant bacteria
In this study, antibiotic resistance test was performed for 18 types of the bacteria isolated from the air of different wards of the hospital. The antibiotics selected in this study were as follows: ce xime, amoxicillin, azithromycin, gentamicin, doxycycline, cipro oxacin and sulfamethoxazole. The bacteria were cultured on tryptic soy agar (TSA) medium containing seven types of the antibiotics. The prepared media containing the desired bacteria were transferred to plates, and two antibiotic discs were placed inside each plate.

Bacterial identi cation by PCR method
The total genomic DNA of the bio-aerosol samples were extracted by standard phenol-chloroform method as described elsewhere (Krumins et al. 2014). UV spectrophotometry was used to quantitative and qualitative analysis of extracted DNAs at 260 and 280 nm, respectively. 16S ribosomal-ribonucleic acid polymerase chain reaction (PCR) was applied for bacterial identi cation in culture-positive samples. Universal oligonucleotides primers speci cally designed for detection of 16S rRNA gene region were used (Mulla et al. 2018): Forward: 27f (5'-AGAGTTTGATCMTGGCTCAG-3'); Reverse: 1492R (5'-GGTTACCTTTGTTACGACTT-3'). For ampli cations of 16S ribosomal-DNA, reaction mixtures contain around 100 ng of template DNA, 12.5 µL of 2x PCR master mix containing appropriate PCR buffer, 2.5 mM concentration of each dNTPs, 0.2 units/µl Ampliqon Taq DNA polymerase, 1.5 mM of MgCl 2 and a 20 pmol of each forward and reverse PCR primers in a total volume of 50 microliters were prepared. In each PCR run, a negative control consisted of all PCR components except for template bacterial DNA. The PCR conditions were as follow: after 5 min initial denaturation step at 94˚C, 33 cycles of denaturation for 30 seconds at 94°C, annealing for 30 seconds at 55°C, and extension for 90 seconds at 72˚C, followed by a nal extension for 10 min at 72˚C were run in a thermal cycler machine (Biometra, Germany). The ampli cation products were electrophoresed in 1.5% agarose gel at TBE and visualized using a UV transilluminator.
The PCR Products were gel puri ed by QIAquick PCR puri cation kit and Sanger sequencing were done by Microsynth (Switzerland). Sequence editing and assembly were done by DNA Dragon 1.6.0 (http://www.dna-dragon.com/). Multiple sequence alignment was carried out by clustal W method (Thompson 1994) in MEGA X (MEGA and Evolution).

Fungal identi cation
The fungal samples were incubated at 25 to 27°C for 72 h. After this period, the number of colonies on the plates was counted. For the initial differential identi cation of fungi, their macroscopic features including surface and back staining of colonies and their microscopic characteristics including shape, size and location of spores were used.

Modeling the dispersion of concentrations of bio-aerosols in different wards
Modeling methods are commonly applied to project the dispersion and distribution of contaminants in environments. SURFER is a contouring and 3D surface mapping software program running under Microsoft Windows. This software quickly and easily converts data into outstanding contour, surface, wireframe, vector, image, shaded relief, and post maps. The SURFER software is a data dispersion modeling software, which can be applied in different areas. This software can predict and test data using the power training from input data. The data dispersion in this method is determined on the basis of different counters and layers of data. In this method, the data dispersion and their scale are determined by the coloring. In this study, 70% of the data were used for training the networks, 30% were used for testing the software and predictive model.

Statistical analysis
Pearson correlation coe cient at a signi cant level (α = 0.05) was used to establish the relationship between the bacteria and fungi concentrations in the air and the parameters such as temperature, wind speed and direction, moisture percentage, number of suspended particles. Meanwhile, the kruska-wallis test was used to determine the possible relationship between the bioaerosol concentration and the change of seasons and location.

Results And Discussion
In hospital environments, various factors such as temperature, relative humidity, hospital building design, ventilation system, and indoor population density and disinfection methods can affect the concentration of air pollutants (Mousavi et al. 2019). In this study, a total of 262 samples of bacteria and fungi from 10 hospital wards were examined. As a result, 14 bacterial species and 12 fungal species were identi ed.
Particle distribution in different wards of the hospital Particle density in different wards of the hospital is in uenced by factors such as the number of beds in each room, the number of patients in the hospital room, the rate of ventilation, the number of staff and the proximity to a street (Shokri et al. 2016). Due to the effect of particles on the density of bacterial and fungal bioaerosols, the sampling time of suspended particles coincided with the fungal and bacterial sampling. The results of this study showed that the average particle concentration in about 90% of the hospital wards and ambient air was higher than the 24-hour World Health Organization (WHO) and United States Environmental Protection Agency (USEPA) standards, which are and, respectively. In accordance with our observations, Rezaei et al. reported the concentration of PM10 and PM 2.5 suspended particles in the air of some wards inside the air around a hospital in Tehran above the recommended limits of the WHO and USEPA and stated that the quality of indoor air was affected by the ambient air (Rezaei et al. 2013).
In this study, the effect of temperature as one of the meteorological parameters on the concentration of suspended particles was investigated. Based on the results, the average temperature of the hospital wards was 24.77°C. Centers for Disease Control and Prevention (CDC) and Healthcare Infection Control Practices Advisory Committee (HICPAC) recommend temperatures of 21-24°C and 23-27°C, respectively, in winter and summer for most wards of hospitals (Chinn &Sehulster 2003).
In the infectious part, in all concentrations studied, temperature and particle concentration had a signi cant relationship and a positive correlation coe cient, i.e. with increasing temperature in the infectious part, the concentration of suspended particles increased. This increase in the concentration of particles in the ICU and infectious wards can be due to reasons such as the large number of patients admitted to the ward, high tra c of companions, use of non-sterile personal equipment by companions and patients, lack of proper ventilation system, and type of disease. Therefore, temperature can be considered as a factor in increasing the concentration of particles. Shokri et al. reported a signi cant positive relationship between the temperature and humidity and the concentration of suspended particles in the sizes of 0.3, 2.5 and 10 µm in indoor air (Shokri et al. 2016).
According to the results, there was no direct and signi cant relationship between moisture and particle concentrations in different diameters in all the wards. The most polluted part in terms of the presence of particles in different sizes was related to the emergency ward for reasons such as a wide range of patients and their congestion in the emergency ward compared to other wards or high tra c of clients, lack of hygiene, smoking and inadequate ventilation. Unlike, it was found that the operating room be tted from the best conditions, which can be due to the high level of health standards such as limited tra c, fewer patients, closed entrance to the other wards and proper ventilation, sterilization and disinfection of surfaces and premises. In agreement with our study, Nikpei et al. reported that the highest number of particles with diameters of 0.3 and 2.5 µm was for the emergency ward (Shokri et al. 2016).

Fungi
According to the data from Table 1, the lung ward was the most infected part of the hospital in terms of the presence of airborne fungi. Even so, in this section, the number of colonies was higher than 200 CFU/m 3 . Also, the operating room with the lowest number of grown colonies had the best air quality among the other wards of the hospital. The low level of pollution in the operating room can be due to the importance and sensitivity of this ward compared to other wards inside. The hospital has a high level of compliance with health standards such as limited tra c, fewer patients, frequent puri cation of room air by high-e ciency particulate air (HEPA) lters, suction of outside air by exhaust fan and sterilization of equipment and surfaces by ultraviolet devices.
In this study, the number of colonies measured in different wards of the hospital was higher than the standard recommended by the WHO, which is 50 colonies. Although the health hazards posed by bioaerosols have been identi ed and proven, no speci c permissible limits are recommended for this category of airborne pollutants and the values provided are the recommended values. The large number of hospital beds and the consequent increase in the number of patients and visitors, as well as the  The reason for the predominant presence of these three types of fungal species in the air inside the hospital can be stated that Penicillium, Cladosporium and Aspergillus fungi have high growth ability in different climatic conditions and by producing small, light spores remain in air. Conidia spores of these fungi also have an outer layer rich in hydrophobic protein, which leads to their further suspension in the air. These fungi have the ability to supply the carbon and hydrogen they need from a variety of sources, allowing them to survive longer in a variety of conditions. However, other fungi such as Alternaria and Ulocladium and some other fungi produce smaller, larger and heavier spores that tend to settle faster and are found at different levels (Alangaden 2011,

Vonberg &Gastmeier 2006).
The most and least fungal species observed in the present study were Penicillium and cranosporium and yeasts and scopolariopsis (Fig. 1). Several species of fungi have been observed in some stations. Fungal species of Aspergillus avus, Alternaria, Penicillium and Geotrichum were mostly observed in the burn ward. In the ICU ward, Alternaria, Aspergillus niger and Ulocladium were mostly observed. Furthermore, in the emergency ward, the most observed species were Cladosporium, Penicillium, Rhizopus and Ulucladium.

Bacteria
Bacterial densities in the hospital wards ranged from 3.75 to 214.2 CFU/m 3 . According to the results presented in Table 2 It should be noted that the average density of bacterial bioaerosols in the men's and women's wards, lungs and burns was higher than the standard recommended by the WHO (100 CFU/m 3 ) (Fig. 2). According to the study by Valedeyni Asl et al., the density of bacterial bioaerosols in the air of Ardabil teaching hospitals was higher than the standards suggested by the WHO and USEPA.
Factors such as population density, ventilation and health conditions of the building and the type of hospitalized patients, the presence of companions and staff can increase the density of bacteria compared to the proposed standard (VALEDEYNI et al. 2018). Considering that Tohid Hospital in Sanandaj is an educational and medical center, it can be said that one of the reasons for the high density of bacterial bioaerosols in this hospital, in addition to the high volume of patients, can be the presence of many students. In Masoudinejad's study, a signi cant linear correlation was observed between patients and population density with the concentration of bacteria, which showed the larger the population, the higher the number of bacteria in the air (Massoudinejad et al. 2015).
Environmental parameters are one of the factors affecting the microbial population in hospital environments. Due to the fact that temperature changes in the studied areas are in the small range (24 to 25), it does not have a signi cant effect on the concentration of bacteria. Also, the lack of correlation between the percentage of relative humidity and the number of bacteria in this study can be attributed to the small range of relative humidity changes (23)(24)(25)(26)(27) at the sampling points, which is 40 to 60% less than the proposed standard (Ra ee et al. 2018).
Since only oors, walls and some pieces of equipment are washed with disinfectants when washing and disinfecting parts, the humidity of the air can increase due to washing, which facilitates the growth and persistence of microorganisms. On the other hand, if air conditioning is used in hospitals, it can reduce the humidity; because humidity is effective in the growth of bioaerosols and if air conditioning is used, bioaerosols that are in the outside air do not penetrate into the indoor environment and therefore the amount of indoor air pollution will be reduced. As it turns out, different ndings have been presented regarding the effect of temperature and humidity on the growth of bacteria in the air of hospitals, which requires more and more detailed studies in this eld.
It was found that there was no signi cant relationship between the number of particles observed in different sizes and concentrations and the number of bacteria observed. That is, particle concentrations and different particle sizes had no effect on the microbial load. The ndings of this study are inconsistent with some previous studies. Mirhosseini et al. reported that there was a signi cant relationship between 1 to 5 µm particles and the density of bacterial bioaerosols in the surgical and ICU wards (Mirhoseini et al. 2015).
According to the results of differential tests, most of the bacteria isolated from the air of the wards in Tohid Hospital was Staphylococcus hemolyticus (Fig. 3). In a study by Solomon et al Staphylococci are among the opportunistic microorganisms that are detected in most areas, and since Staphylococcus species are part of the natural ora of the skin and nose, it seems that their high rate in this study due to the increase in population, especially during the presence of companions. Coagulase-negative staphylococci include species of the genus Staphylococcus that lack the coagulase enzyme, and the most important species are Staphylococcus epidermidis, Staphylococcus saprophyticus, and Staphylococcus hemolyticus. These species are not highly toxic, but are an important cause of infections in high-risk groups.
Staphylococcal infections can be transmitted through contact with an infected person or the patient's belongings, including clothing, towels, and bedding. In this study, Escherichia coli was less common than Staphylococcus, Bacillus and Pseudomonas. It has been documented that Escherichia coli is involved in the development of diseases such as urinary tract infections, sepsis, pneumonia, gastroenteritis and meningitis (Sivagnanasundaram et al. 2019).
According to the results, the total average of bioaerosols in this hospital was 184.38 CFU/m 3 . The highest density of bioaerosols was in the lung ward with the amount of contamination (336.67 CFU/m 3 ) and the lowest was in the operating ward with the amount of contamination (15.25 CFU/ m 3 ). Following that, the women's ward and then neurology had the highest pollutant density.

Evaluation of bacterial resistance to antibiotics
The results of antibiotic resistance of 18 common bacteria detected in this study have been presented in Table 3. Among them, the highest drug resistance was observed in Staphylococcus hemolyticus and aureus. Staphylococcus hemolyticus had shown resistance to ve types of GM-CP-AZM-AMX-CFM antibiotics. Staphylococcus aureus is a ubiquitous organism and has a high potential for causing various diseases in humans due to its high resistance to adverse environmental conditions. The development of resistance to various antibiotics in strains of Staphylococcus aureus causes many problems in the treatment of diseases related to these microorganisms, thus, it is necessary to know the pattern of resistance of these microorganisms in the treatment of related diseases (Saha et al. 2008). Antibiotic resistance of Staphylococcus aureus to GM-AMX-CFM antibiotics has been observed. In the study by Saadat et al., the highest resistance of Staphylococcus aureus to amoxicillin was found, which is close to the ndings of this study (Saadat et al. 2014). Also, Staphylococcus epidermis was resistant to CP, GM and CFM. In the study by Nourbakhsh and Momtaz, Staphylococcus epidermis was the most resistant to the antibiotics erythromycin, cipro oxacin, clindamycin and tetracycline, which is consistent with the results obtained in the present study (Nourbakhsh &Momtaz 2016 5).
Modeling the dispersion of pollutants using SURFER software Maps prepared based on data from particle measuring stations in lung, neurology, infectious and open air wards showed that the emission and concentration of pollutants in the eastern parts had a higher dispersion. In other areas, including burns, ICU, emergency and men's and women's wards, the distribution of pollutants in all measuring stations in these areas was high. According to the results, the entrance of the infectious ward (east side) has the highest particle density, which can be due to the location of the waiting room at the entrance of the ward and high tra c in these areas (Fig. 6). However, the distribution of pollutants in other wards was evenly distributed.
Counter curves on the maps related to the distribution of bacteria in the hospital wards showed that in the men's and women's wards, the concentration of bacteria in the stations located in the northern and central parts of the wards was higher than the southern parts. The number of bacteria in the operating room was measured in the range of 2-36 CFU/m 3 . The counter curve numbers show that the bacterial dispersion was lower in most parts of the measuring stations and the less contour lines in the section. The central part shows the high concentration of bacteria. In the previous sections, it was stated that the lowest bacterial density was in the operating room.
In the intensive care unit, bacterial densities were measured in the range of 72-128 CFU/m 3 , and counter curves in the bacterial spreading map in this ward showed that bacterial densities were measured at the measuring points in the western part of the ward, which is located at the entrance to the ward, was more than the eastern parts (end of the ward). Figure 7 shows the possible spread of bacteria in some parts of the hospital.
According to the maps obtained from the spreading of bacteria in the intensive care unit (Fig. 7), the density of these microorganisms in the measured points located in the western part of the ward (entrance part) was more than the eastern parts (end of the ward). Due to the proximity of the entrance of the two infectious diseases and special care, the high presence of particles and bacteria in this area can be due to high tra c and lack of natural and arti cial ventilation in this place.
The fungal spread distribution map in the intensive care unit shows that the rate of spread and dispersion of fungal aerosols is higher in the measuring points located in the western part and ow of pollutants has decreased while moving to the central and eastern (end of the ward). This situation indicates the concentration of fungi in the western part (entrance) of the intensive care unit. As mentioned above, the spread of bacteria has been higher in the intensive care unit in the western part. The following gure (Fig. 8) shows the possible spread of fungi in some parts of the hospital.
One of the reasons for the high presence of pollutants at the entrance of the ICU can be the lack of proper and adequate ventilation in this area, as well as the high tra c of the population and patients. On the other hand, in multi-bedroom wards of the hospital, including the intensive care unit, because there is a risk of infection of neighboring patients, reasonable measures should be taken to control the infection. In a study by Ching et al. carried out on reducing the risk of airborne infections in hospitals using hospital curtains, hospital curtains were called as physical barriers to disease transmission is potentially a simple but effective way to reduce the risk of infection; in this study, the effectiveness of hospital curtains in preventing the transmission of airborne diseases in hospital rooms has been investigated using numerical modeling. Among all case studies, it was found that the use of curtains between two beds can reduce the peak contaminant concentration for each neighboring patient in a bioaerosol dispersion process by up to 65% (Ching et al. 2008).

Conclusion
According to the results obtained, the general average of the bioaerosols in the hospital studied was 184.38 CFU/m 3 . The most densities of the bioaerosols were observed in the lung ward (336.67 CFU/m 3 ), followed by the women and neurology. And, the least density was seen in the operation room (15.25 CFU/m 3 ). It was found that the air quality in some wards of the hospital did not have a suitable status. Although the hospital bene ts from a central ventilation system (exhaust fan), which covers all the wards, the system may suffer from a suitable operational and executive standard. Therefore, the system should be assessed closely in terms of principles of ventilation design. Since the Ecofan system and suction of inside air to outside and for ventilation and the entrance of fresh air to the inside, natural air without any pretreatment is used, thus, the quality of the inside air may be impacted and pollutants may be entered. Since the hospital lacks a suitable guideline and standard regarding the concentration of bacterial and fungal pollution inside the hospital air, it is vital to pay adequate attention to employ these standards by the responsible authorities. Most of the hospitals in Iran, like the hospital studied in the current research, lack a system for air treatment; therefore, enough equipment should be installed. Naturally, other affecting parameters like the standard of the number of beds to area, the physical sanitation of the hospital environment, optimum use of disinfectants, periodical disinfection of air ow path and channels to prevent microorganism growth and the training of staff should be taken into account.

Declarations
Ethics approval and consent to participate   Possible dispersion of fungi in the ICU ward of the hospital