question: Background and aims: Over the past year, millions of people around the world have infected with the COVID-19 virus The SARS-CoV-2 replicates efficiently in the human upper respiratory tract Infected people produce large amounts of the virus in their upper respiratory tract during an introductory period, which leads to more spread of the virus to other people The World Health Organization (WHO) has suggested that acute respiratory syndrome SARS-CoV-2 is transmitted through person-to-person transmission and contact with contaminated surfaces However, the rapid spread of the disease suggests that other routes, such as airborne transmission, may play a role Several research studies have been performed to evaluate the possible transmission of the virus through the air Although some studies have found no evidence of airborne transmission, recent work has confirmed the presence of SARS-CoV-2 even in public places Experience and knowledge of the mechanism of similar viruses such as SARS-CoV also support this hypothesis During COVID-19 pandemic, while the hospitals can be one of the most important centers in providing health care services, due to the inappropriate air ventilation and purification system, high traffic of people;some of them have been introduced themselves as one of the most high-risk sources of SARS-CoV-2 transmission The present study aimed to assess the SARS-CoV-2 in the air and surfaces of ICU ward in one of the designated hospitals in Tehran So that, in addition to determining the possibility of inhalation and contact exposure in ICU, which is the main ward for presenting special medical care to patients with severe acute respiratory infections, it aimed to assess a hypothesis of SARS-CoV-2 airborne transmission Methods: This cross-sectional experimental study was performed on April 29, 2020 in the Covid-19 ICU ward in one of the designated hospitals, Tehran, Iran The area of ward was 50 m2 and has seven beds, all of which were occupied at the time of sampling, and five medical staff were involving there All patients were equipped with oxygen masks and all the staff used all conventional personal protective equipment such as Honeywell-75FFP100NL respirators On average, surface disinfection was performed three times a day The general ventilation system included the ceiling diffuser to supply fresh air into the room and wall-mounted exhaust vent and did not use natural ventilation (such as opening the window) It should be noted that the exhaust system did not work well at the time of sampling This study was carried out in two phases including surface and air sampling Impinger method was applied to air sampling Thus, at a distance of 1 5 to 1 8 meters from the ground, the air of the ICU ward was passed through a sampling pump with an flow rate of 1 5 l/min into the porous midget impeller-30 ml containing 15 ml of virus transmission medium (PVTM) for 45 minutes To reverse the presence of SARS-CoV-2 in air samples, the reverse polymerase chain reaction (RT-PCR) reaction method was used Sampling of surfaces was done with the help of swabs impregnated with the solution of the Viral Transport Medium from a certain area (25 cm2) from the desired part and putting it inside the vial containing the transfer medium (protein stabilizer, antibiotic and buffer solution) They are also were analyzed by RT-PCR technique Prior to sampling, all laboratory equipment used was sterilized and autoclaved using a 70% alcohol solution according to the US Centers for Disease Control and Prevention (CDC) protocol The air sampling was done at a distance of 1 5 to 2 meters from the patient's bed The devices used to measure temperature, humidity and air velocity were multi-purpose anemometer (China BENETE, GM8910,) and air pressure, digital barometer (AIRFLOW, DB2, USA) The mean parameters of weather conditions included: air temperature 24 ° C, humidity 35%, air pressure 1005 mb and air velocity of 0 09 m / s Results: Of the ten air samples, 6 were positive (60%), with the highest RNA concentrations observed at the point between beds 6 and 7 (3913 copies per ml) Most of the reported negative air samples were from the middle of the ward, which was further away from the patients' beds The mean RNA concentration of the virus was obtained 820 ± 2601 copies per milliliter In addition, of ten samples taken from different surfaces of the ward, 4 samples were positive (40%) and the highest concentration (8318 copies per ml) was related to the table next to bed number 3 All positive samples were observed close to the patient's bed, and the mean RNA concentration of the virus was 3227 ± 3674 copies per milliliter Conclusion: The results of the study indicated that the virus was present in the inhaled air of the ward and its surfaces, especially in areas close to the bed of patients These findings underscore the airborne transmission of the virus along with other ways of transmission, such as person-to-person contact and contact with contaminated surfaces Due to the environmental pollution of the studied ICU ward to the SARS-CoV-2 virus, the effective implementation of air isolation methods such as the use of respiratory protection equipment (N95 mask) and powered air-purifying respirator as well as ensuring the correct function of hospital ventilation systems and improving it, is essential for the protection of health care staff Health care workers need to be continuously monitored and screened from a COVID-19 perspective, and infection prevention and control protocols (IPCs), such as respiratory protection, regular cleaning of the environment, and effective disinfection of areas have been implemented In the case of the virus, the spread of the disease through both direct methods (drops and person-to-person) as well as indirect contact (contaminated objects and airborne transmission) has almost been proven, which reaffirms the need for precautionary measures regarding airborne isolation against the virus It has been suggested that in order to more accurately assess the transmission behavior of the virus, similar studies but longitudinal ones have been done from the admission to discharge of the patients in different wards of the hospitals Moreover, the role of natural and mechanical ventilation systems more comprehensively examined in the presence of airborne virus © 2020 Iran University of Medical Sciences All rights reserved