Determination of air exchange in rooms. General information about ventilation. Determining the required air exchange
The release of harmful substances in the premises can occur continuously, intermittently or for a short time.
With the continuous intake of harmful substances, the reduction of their concentration to an acceptable value is achieved by the continuous removal of polluted air from the room and the supply of clean (outdoor) air into it. This change of air is called air exchange. In case of periodic or short-term exposure to hazards, they are removed by periodically extracting polluted air from the room and supplying clean (outdoor) air to it.
Competing Interests: The authors have stated that there are no competing interests. To prevent contamination of the surgical site, airborne concentrations in operating theaters must be reduced. Air quality in operating theaters and surrounding areas is also important to healthcare workers. Therefore, this study assessed air quality in the recovery room, areas surrounding the operating theater area, and operating theaters in the medical center.
Determining the required air exchange
Temperature, relative humidity and carbon dioxide, particulate matter and bacterial concentrations were monitored weekly for one year. The measurement results show clear differences in air quality in different operating room areas. In conclusion, air quality in the recovery room and operating rooms requires attention and deserves long-term surveillance to protect both surgical patients and healthcare workers. Hospital indoor air pollution is associated with inadequate building conditions, including Construction Materials, air conditioning systems, ventilation rates and human factors such as overcrowding in a confined space.
When highlighting a large number hazards requires an intensive change of air, with the release of a smaller amount of hazards, less intense. The intensity of air change is characterized by the air exchange rate, which is the ratio of the amount of air L (in m3) supplied or removed from the room per hour to the internal volume of the room V (in m3).
Air quality assessments in the working test assessed levels of particulate matter, microbial agents, and volatile organic compounds. Employees, patients and visitors are significant sources of airborne microbes in hospitals. The frequency with which people enter and leave operating theaters can also increase the number of microorganisms in the premises. Therefore, the concentration of microorganisms in the air must be reduced to prevent contamination of the surgical site. In order to evaluate the operating environment for surgical patients, a previous study assessed variations in hospital indoor air quality across eight operating rooms at a medical center in northern Taiwan.
The air exchange rate shows how many times the air in a given room is replaced within an hour. Most of the premises of public catering enterprises (washing, harvesting, office) are characterized by a constant intensity of harmful emissions. Therefore, for them, norms for the frequency of air exchange can be established both in terms of inflow, i.e., by the amount of supplied outside air, and by exhaust, i.e., by the amount of polluted air removed
Method for determining the required air exchanges in the premises
In addition to surgical patients, air quality in operating rooms is also critical for healthcare workers. Reports have identified an increasing number of adverse health effects associated with time spent in mechanically ventilated buildings, typically in the workplace. Symptoms are usually associated either with exposure to a combination of substances or with increased individual susceptibility to low concentrations of pollutants.
The amount of inlet or extract air based on the air exchange rate is determined by the formula
For most rooms, the multiplicity of inflow and exhaust is different. This is done in order to exclude the possibility of air entering from more polluted rooms to less polluted ones, for example, from sanitary facilities (latrines, showers) to industrial premises.
Compared to operating theaters, more medical workers and surgical patients were present in the postoperative rehabilitation departments. Therefore, this study is the first to evaluate long-term changes in air quality in operating rooms, including operating rooms, post-operative recovery room, and other nearby locations in a medical center.
Permissions for this study were obtained from Chang Gong Memorial Hospital. Figure 1 shows the operating theater area. The postoperative recovery room is in an open space and is adjacent to the kidney transplant room. The tool room is next to the laundry room and the restaurant. The exit from the laundry room is next to the restaurant. The trauma surgery room is located next to the office. The liver transplant room and the delivery room are located on the left and on the corner of the operating room area, respectively.
To do this, rooms with less polluted air (for example, salesrooms, corridors, lobbies) are supplied with more supply air, as a result of which they create high blood pressure(backup) and the air from the clean room enters the adjacent with more polluted air, from where it is removed.
In hot "shops (kitchens, confectionery shops), as well as in trading floors, depending on the nature of the technological process, the equipment used, the volume of rooms, the number of people and the mode of operation, different amounts of heat, moisture, and gases are released. To remove them, a different amount is required ventilation air Therefore, the air exchange in the listed premises must be calculated according to the amount of harmful substances emitted.
During the sampling period, the indoor air was conditioned but not heated. Ceiling-mounted high-efficiency air filter air filter with 15 air changes per hour provided coverage operating systems but did not serve the office and delivery room. The office only had an exhaust air filter that was cleaned at 4 month intervals, while the delivery room had an exhaust vent design without a filtration system.
Indoor air in the operating theater area was sampled once a week for one year. The duration of air monitoring was 60 minutes in the morning at each location. Air was bled from operating theaters during operations. Air sampling devices were placed approximately 5 m away from operating tables to avoid aseptic area contamination in operating rooms during surgery or were placed in the center of each sampling area, such as in the post-operative recovery room and areas surrounding the theater operating area .
Air exchange to remove harmful gases and vapors is determined by the formula
Calculation of air exchange for removal carbon dioxide. To remove carbon dioxide (CO2) into the room is introduced outside air with low CO content. This air absorbs some of the carbon dioxide and other harmful gases that accompany it, and then is removed using exhaust ventilation.
All instruments were positioned 2-5 meters above the floor to simulate the respiratory zone of medical workers. The doors of the operating theaters and areas surrounding the operating room were always closed during the sampling period. Gram-negative bacteria and Gram-negative bacteria have been identified biochemically. The chi-square test was used to determine differences in airborne bacteria shedding rates at different sampling locations in the operating room area. Pearson correlation analysis was used to determine the relationship between two continuous variables with normally distributed data.
The amount of air that needs to be changed in the room within an hour to remove carbon dioxide is determined by the formula
The amount of carbon dioxide emitted by people, as well as its content in the outdoor air, does not depend on the season, so the amount of air exchange calculated to remove carbon dioxide will be the same throughout the year.
Such mixed effect models have the advantage of adjusting invariant variables with fixed effect models and taking into account individual differences according to random effects models. Analytical results show that all air quality indicators differed markedly in different locations surrounding the operating room.
The frequency of isolation of bacterial species varied markedly among different locations within the coverage area of the operating theaters. The shedding of Gram-negative bacteria exceeded that of Gram-negative bacteria in the operating room area. This is the first study in Taiwan to use air quality indicators in the operating room area, including the post-operative recovery room and surrounding areas in a medical center, to document differences in air quality. Until recently, there was no international consensus on best method and frequency of air sampling and allowable bioburden in operating areas.
When other harmful gases are released into the room, the amount of ventilation air is calculated according to the same formula, only in this case Рpr = 0.
IN winter time the outside air is heated up to the supply air temperature. For trading floors, this_temperature is assumed to be 14°C, for kitchens - at least 12°C, and for other premises -16°C. Outside air temperature for calculation supply ventilation in winter is taken equal to average temperature of the coldest month at 13:00 and is called the outside temperature for calculating ventilation in winter
Thus, the interval between samples was determined by each institution using available funds. However, few countries have set limits for bacteria in conventionally ventilated operating theaters. The results obtained in this study show that the postoperative recovery room had the highest concentration of airborne bacteria. Thus, the impact of bioaerosol on surgical patients and healthcare workers in the postoperative recovery unit requires additional attention.
In accordance with the requirements of Table. 1 air temperature in summer time V working area premises with insignificant heat emissions (trading floors) should not exceed the design temperature of the outside air by more than 3 ° C, and rooms with significant heat emissions - by more than 5 ° C.
Calculation of air exchange to remove excess moisture. At a room temperature of more than 25 ° C, air with high humidity causes people to feel unwell. In winter, high indoor air humidity is unacceptable, since water vapor can condense on the cold surfaces of external fences (windows, doors, attic ceilings). At the same time, drops from the ceiling, moistening of building structures and, ultimately, their destruction are observed. Therefore, the relative humidity in catering establishments should not exceed: in kitchens and washing rooms - 60-70%; in cooled chambers - 80-90%; in confectionery and pie shops, as well as uncooled warehouses - 60-75%; in other rooms - 65-70%.
In this study, the results of the correlation analysis indicate that the number of people in the operational control area correlated with the concentrations of bacteria in that area. We hypothesize that variations in airborne bacterial concentrations depend on sampling sites with different functions in the operating room area of a hospital. In addition, proper staffing and discipline can minimize the spread of bacteria in medical personnel and reduce airborne contamination of microorganisms.
The use of cleanroom standards based on the presence of air particles can be considered a routine procedure for monitoring the distribution of bacterial concentrations in operating room areas. This result is consistent with the results of a previous study. The distribution of microbial species in the operating room area, especially in the post-operative recovery room and operating rooms, requires attention from the environmental safety and health departments of hospitals to reduce the risk of exposure to surgical patients and healthcare workers.
To remove excess moisture, air with a low moisture content is supplied to the room. By absorbing water vapor, the air is humidified, after which it is removed using exhaust ventilation.
The amount of air that must be supplied to the room to remove excess moisture is determined by the formula
In summer it is determined at the supply air temperature Pr, in winter - at the outside temperature to calculate the ventilation t„ B.
Vibration, production noise
Various factors influenced sampling results environment, which cannot be constant over time. Long-term monitoring of air quality in operating rooms, especially in the post-operative recovery room and operating theaters in hospitals, is needed to ensure a safe environment for surgical patients and working conditions for hospital staff. Previous research has shown that ventilation systems are a source of infection; in some cases, the systems spread infectious pathogens.
Air exchange is determined as follows:
1. Calculate the excess heat release (the sum of sensible and latent heat in kcal / h), moisture Cvl (in kg / h) and the heat-humidity ratio E.
2. According to the known parameters of the supply air tap and fpr, a point corresponding to the beginning of the process is plotted on the /-d diagram, and a beam of the process E is passed through it.
Heat gain from people
Thus, the frequency of cleaning and maintenance for ventilation systems in areas of operating areas can be adjusted depending on the operating time of the system and the number of passengers in the area. In conclusion, air quality in operating room areas, especially in recovery rooms and operating rooms, deserves attention and requires long-term surveillance by environmental and health departments in hospitals to protect both surgical patients and healthcare workers.
3. At the point of intersection of the process beam with the line of the permissible relative humidity of the outgoing air, fx, the outgoing air parameters tyx and /yx are found, or at the intersection of the process beam with the outgoing air temperature line, relative humidity air<руж и его теплосодержание /ух.
The amount of ventilation air is determined by the formula
Ted Cloy is appreciated for his editorial assistance. The authors would like to thank the National Science Council of the Republic of China, Taiwan for financial support of this research under contract no. The financiers played no role in the design of the studies, the collection and analysis of data, the decision to publish or prepare the manuscript.
Indoor air quality in the workplace is a subject of much attention these days, and for good reason. Indoor air quality can significantly affect the health, comfort and productivity of residents. Most passengers hardly notice that indoor air quality is “good,” but most people often recognize when the air is bad. This includes the physical characteristics of air: the amount of air movement, its temperature and humidity.
In industrial premises, the air is polluted with various foreign impurities: harmful substances, dust, excess heat. These secretions create unfavorable conditions for workers and can cause illness. One of the ways to maintain clean air in the premises that meets sanitary and hygienic requirements is general ventilation.
Ventilation complies with current guidelines set forth by the American Society of Heating, Refrigeration and Air Conditioning Engineers Standard 1, Ventilation for Acceptable Indoor Air Quality. Mechanical equipment and building surfaces are kept hygienic. Significant emission sources such as large copy machines are separated from occupied premises and air intakes. Major sources of chemical or biological contamination are quickly identified and controlled. Occupied areas are regularly cleared and efficient housekeeping practices are applied. Operations, maintenance and construction activities are carried out in a manner that minimizes passenger exposure to airborne pollutants. The most common complaint is related to temperature: the air is too hot or too cold.
3 Determining the required air exchange in the premises The required air exchange in the premises is determined by the following factors: the number of people in the room, the release of harmful substances, excess heat. To obtain reliable data, when determining the required air exchange, it is necessary to take into account all these parameters and take the highest value for the calculated value, according to which the ventilation unit is selected.
3.1 Determination of the required air exchange in the room, depending on the number of people in it The required air exchange in the room, depending on the number of people in it L, m 3 / h, is determined by the formula
L = n ∗ L , (1)
where L is the required air exchange in the room m 3 / h; n is the number of people in the room; L'- air consumption per 1 person, depending on the volume (V) of the room, m 3 / h. When V is less than 20 m 3 per person, L′ is taken equal to 30 m 3 / h. With V more than 20 m 3, not less than 20 m 3 / h, and in the absence of natural ventilation, L′ is taken equal to 60 m 3 / h.
3.2 Determination of the required air exchange for the release of harmful substances The required air exchange for the release of harmful substances L , m 3 /h, is determined by the formula qv qpr G L − = , (2) where G is the amount of harmful substances emitted in the room. mg/h; qv qpr, - the concentration of harmful substances in the exhaust and supply air, respectively, mg / m 3. The concentration of harmful substances in the supply air should be minimal and should not exceed 30% of the maximum allowable concentration (MAC) in the air of the working area. If several harmful substances of unidirectional action are simultaneously released in the room, their concentration q, mg / m 3 is determined from the expression q \u003d q1 / MPC + q2 / MPC + ...... + qn / MPC
87. Vibration, industrial noise.
Vibration- these are mechanical vibrations of machines and mechanisms, which are characterized by such parameters as frequency, amplitude, oscillatory speed, oscillatory acceleration. Vibration is generated by unbalanced force effects that occur during the operation of machines.
When studying the vibrations of the human body, it is customary to distinguish between the general vibration of the whole body (transmitted through the supporting surfaces) and local vibration (transferred to the hands when working with manual machines).
To weaken the transmission of vibration from sources of its occurrence to the floor, workplace, seat, handle, etc. Vibration isolation methods are widely used in the form of vibration isolators made of rubber, cork, felt, asbestos, and steel springs.
Vibration damping is the damping of vibration due to active losses or the conversion of vibrational energy into its other forms, for example, into thermal, electrical, electromagnetic. Vibration damping can be implemented in cases where the structure is made of materials with large internal losses; vibration-absorbing materials are applied on its surface; contact friction of two materials is used; structural elements are connected by cores of electromagnets with a closed winding, etc.
The most effective means of protecting a person from vibration is to eliminate direct contact with vibrating equipment. This is done through the use of remote control, industrial robots, automation and replacement of technical equipment. Special footwear with massive rubber soles is used as personal protective equipment for workers. To protect hands, mittens, gloves, liners and gaskets are used, which are made from elastic damping materials.
Noise- this is a set of sounds that adversely affect the human body and interfere with its work and rest.
Sound sources are elastic vibrations of material particles and bodies transmitted by liquid, solid and gaseous media.
The speed of sound in air at normal temperature is approximately 340 m/s, in water -1430 m/s, in diamond - 18000 m/s.
Sound with a frequency of 16 Hz to 20 kHz is called audible, with a frequency of less than 16 Hz - infrasound and more than 20 kHz - ultrasound.
The area of space in which sound waves propagate is called the sound field, which is characterized by the intensity of sound, its speed of propagation and sound pressure.
To reduce noise, various methods of collective protection are used: reducing the noise level at the source of its occurrence; rational placement of equipment; combating noise along its propagation paths, including changing the direction of noise emission, using sound insulation means, sound absorption and installation of noise silencers, including acoustic treatment of room surfaces.
The most effective means is to combat noise at the source of its occurrence. To reduce mechanical noise, it is necessary to repair equipment in a timely manner, replace impact processes with non-impact ones, use forced lubrication of rubbing surfaces more widely, and apply balancing of rotating parts. Reducing aerodynamic noise can be achieved by reducing the gas flow rate, improving the aerodynamics of the structure, sound insulation and installing silencers. Electromagnetic noise is reduced by design changes in electrical machines.
Methods for reducing noise along the path of its propagation by installing soundproof and sound-absorbing barriers in the form of screens, partitions, casings, cabins, etc. have been widely used. Light and porous materials (mineral felt, glass wool, foam rubber, etc.) have good sound-absorbing properties.
