Air condition system design of a facility containing negative air pressure rooms

Clean rooms are working places in which concentration and sizes of air particules are controlled. They are constructed and designed to prevent difussion or penetration of particules and parameters such as pressure, temperature and humidity are also controlled in case of necessity. Currently, they are in use for an extend area from medicine to microchip production. Clean room technology getting more and more important due to the developments basicly in the fields of pharmacy, medicine, electronics, biotechnology, optics, micromechanics and space technologies. A literature search on designing of an air condition system of a facility containing negative air pressure rooms shows that there is significantly less information about negative air pressure rooms comparing positive air pressure rooms. The reason is architecture of facilities contain negative air pressure rooms have differences due to production. As a result, all different facilities require different and specific designs. Because of this, in this study, air conditioning system design of a facility containing negative air pressure rooms explained with the usage of a sample facility. Numerous factors should be taken in to account while designing a clean room. For air condition system design of a facility, all devices and units that affect mechanical installation should be well known, for instance; autoclaves, disinfection units, airlocks, gas tight doors. Moreover, for designing an air condition system, all necessary units and devices and their working principles should be known. For this project, this units, and devices are hygienic air handling unit, air filters, constant air volume units, variable air volume units, safe houses, fans, heat recovery units, and heating and cooling coils. The designing steps of an air condition system are giving space numbers to every space in facility, getting information for all building materials, determining the units (air handling units, hygienic air handling units, exhaust fans, fresh air fans, heat recovery units etc.) to use in design, getting information about classes of spaces from the GMP Expert, determining air leakage directions, calculating the pressure values of all spaces, calculating air volume rates between spaces, preparing a schema of air condition system, calculating heat loss and heat gain of all spaces, calculating fresh air and extract air volume rates, determining air volume rates of units, adding all units on plans, drawing the ducts and other necessary devices (CAV, VAV etc.), calculating the pressure loss and choosing units. In this thesis, air conditioning system of a sample vaccine production facility was desinged by using Excel and BricsCAD programs. Vaccine facilities are working places which must be operated based on negative air pressure clean room principles. There are two areas in the facility. These areas are contaminated area and entrance area. Entrancearea is used for going in and out of staffs and products. Contaminated area includes vaccine production spaces. Air handling units of these two areas are independent. Entrance area air handling unit has a vantilator and an aspirator. Contaminated area air handling units have only vantilators. Extracted air from contaminated area exhausts by fans. Classes of all spaces of the facility determined due to their purposes. This determination is done by a GMP Expert who knows about materials and productions in use or produced. For class determination, the class table in GMP Guide is used. After these procedures, airflow direction is determined between spaces in facility. Airflow directionsmust be from clean rooms to less clean rooms. For this purpose, corridors are used to prevent airflow between spaces. There are two possibilities. Corridors should have higher or lower pressures from their adjacent rooms. After determined airflow directions between spaces, all spaces' pressure values are calculated beginning from the entrance. After this calculation, air volume rate between spaces is calculated. An emprical formula, which is found by Blaser (1994), is used to calculate the airflow rate between spaces. Considering these informations, schema of the air conditioning system is prepared. Before preparation of schema, a duct outline is determined. Supply and extract air volume rates to spaces wrote on schema. To supply maintenance of production contaminated area air handling unit should be back up. For back up two number of contaminated air handling units and two number of exhaust fan chosed. After prepared schema of air condition system's design, units are choiced. Before this, heat loss and heat gain calculations must be done for all spaces in the facility. In this thesis, heat loss and heat gain values are accepted as calculated. Next, supply and extract air volume rates are found. A table is prepared by using all these informations. This table includes space numbers, names, classes, pressure values, number of staffs, overhead lighting powers, electrical equipment powers, space heat gain values, sizes, total heat gain values, heat loss values, cooling ts, air volume rates due to cooling values, numbers of air change due to cooling value, air change rates, supply air volume rates, real cooling ts, air leakages originated from pressure, extract air flow rates for each space. Number of air change is chosen by experience because there is a scientific gap at determining number of air change according to the class of the space. After comparison of number of air change obtained using cooling value and number of air change that was determined by experience, the greater one used for calculations. The operator of the system should perform some tests in all sapces in the facility. By these tests the operator should provide the number of particules in each space due to it's class. Units choice is done by using this table. If one of the air handling units of contaminated area goes out of order, production could maintain by shutting down 20% of system. For this purpose, supply air volume rate required for contaminated area is multiplied by 80% and two seperate air handling units are chosen which can supply this air volume rate. The same ratio is used for extract air volume rate to choose exhaust fans. Backup is not necessary for entrance area because this area is not used for production process. Afterwards, air handling units' configurations of both entrance and contaminated areas are determined. A heat recovery unit is used in the air condition system. By this way, the energy transfer between extract air and fresh air could occur according to the efficiency of the heat recovery unit. As a result, heating and cooling coils' capacities are decreased. After units choice, air volume rates are written on air condition system schema. Ducts must be drawn on determined lines and dimensioned. Next, pressure losses must be calculated for each duct line. In this thesis, duct lines of contaminated area air handling units and exhaust fans are drawn as single track and pressure loss values are assumed as calculated. In this design safe houses are backed up.as contaminated air handling units and exhaust fans. By this means, during routine maintenance, safe house filters can be changed one by one without stopping production process.