HOT AIR OVEN .pptx

Hot air oven instrument

1. HOT AIR OVEN PROJECT Vedanti S. Gharat R oll no. :- 20 Exam seat no. :- 005018 T.Y. B.Sc. Biotechnology

2. INTRODUCTION A hot air oven is a l aboratory instrument  that uses dry heat to sterilize laboratory equipment and other materials.  Hot air oven also known as forced air circulating oven . We can sterilize Glassware (like petri dishes, flasks, pipettes, and test tubes), Powder (like starch, zinc oxide, and sulfadiazine), Materials that contain oils, Metal equipment (like scalpels, scissors, and blades) by using hot air oven.

3. To destroy microorganisms and bacterial spores, a hot air oven provides extremely high temperatures over several hours . The widely used temperature-time relationship in hot air ovens to destroy microorganisms are 170 degrees Celsius for 30 minutes, 160 degrees Celsius for 60 minutes, and 150 degrees Celsius for 150 minutes.  The process of dry heat sterilization using a hot air oven Originally developed by Louis Pasteur . The temperature range of a hot air oven is 50 to 300 ° C. It can be controlled by using a temperature regulator .

4. WORKING PRINCIPLE OF HOT AIR OVEN Sterilization by dry heat is performed by conduction. The temperature is consumed by the surface of the objects, then moves towards the core of the object, coating by coating. The whole object will ultimately attain the temperature needed for sterilization to take place . Dry heat causes most of the injury by oxidizing particles. The primary cell components are damaged and the organism dies. (The temperature is kept for about an hour to eliminate the most ambitious of the resistant spores .)

5. DRY STERILIZATION Hot air oven acts in a manner so that items stored inside the oven don’t grab fire or meltdown . It primarily acts on the principle of structure where heat moves on the outside of the substance and then to the core of the item. (termed a dry sterilization process) While the air shifts hot, it becomes thinner and transfers towards the ceiling of the chamber . If air hits the roof of the chamber it travels towards the ground of the chamber. It helps in the circulation of air within the chamber. This current flow assures the proper and uniform heating everywhere in the chamber.

6. HOT AIR OVEN PARTS AND FUNCTIONS 1. External cabinet :  The External cabinet is made of stainless sheets. It covers the inner chamber . 2. Glass wool insulation :  The space between the inner chamber and external cabinet is filled with Glass wool. It provides insulation to the hot air oven . 3. Inner chamber :  The inner chamber of the hot air oven is made of Stainless steel . 4. Tubular air heaters :  They help to generate heat within the inner chamber. Two Tubular air heaters are located on both sides of the inner chamber . 5. Motor-driven blower :  It helps in uniformly circulating the air within the chamber . 6. Temperature sensor :  It measures the temperature within the hot air oven and displays it on the controller screen . 7. Tray slots : The inner wall of the chamber contains several try slots that hold the trays . 8. PID temperature controller :  It maintains the accurate temperature during the entire cycle. It also controls the temperature and also displays the temperature values . 9. Load indicator :  it indicates the hot air oven is overloaded . 10. Mains on/off switch :  It helps to turn on/ turn off the hot air oven . 11. Safety thermostat :  It is also known as an over-temperature protection device. It keeps your oven and specimen safe in case of controller malfunction.

7. STERILIZATION CONTROL FOR HOT AIR OVEN A ) Biological controls:  10 6  spores of   Bacillus   subtilis  subsp. niger or spores of nontoxigenic strains of  Clostridium   tetani  on paper strips are placed inside envelopes and then placed inside the hot air oven after complete sterilization inoculated in thioglycollate or cooked meat medium and incubated for sterility test under strictly anaerobic conditions for 3 to 5 days at 37°C. Growth in medium indicates the failure of sterilization . B) Chemical control:  Browne’s tube No. 3  which shows a green color after sterilization at 160°C for 60 minutes ( color changes from red to green ). C) Physical control:  Thermocouples and temperature chart recorder used.

8. HOT AIR OVEN PROS/ADVANTAGES No need to water to sterilize the material . Not much pressure is created like autoclave which creates it easy to manage and also makes it safer to work with . In a laboratory environment, it is more fitting to use as compared to other sterilizers . Hot air oven is much smaller in size as compared to autoclaves and also more effective . A hot air oven can be more speedy and higher temperature can be achieved as compared to other means . The operating procedure is simple as compared to other sterilization methods . (quick-drying process ) Its price is low as compared to autoclave. 

9. HOT AIR OVEN CONS/ DISADVANTAGES According to the principle of thermal inactivation by oxidation, it can not slaughter some living organisms, such as prions due to the use of dry heat rather than wet heat . Most of the materials are not fit with hot air ovens such as surgical dressings, rubber items, or plastic material; they can be a meltdown at low temperatures . Glasses may become smoky due to high sterilization temperatures: The temperature holding period is at 160°C for 1 hour, 170°C for 30 minutes whereas at 180°C for 20 minutes . Dry heat penetrates materials slowly and unevenly and thus a time-consuming method because of the slow rate of heat penetration and microbial killing . It requires a continuous source of electricity.

10. HOT AIR OVEN APPLICATIONS It is used to dry glassware, sterilize N95 masks, general instruments, and packaging items in life science, microbiology laboratory . It is also used in chemical and pharmaceutical industries, food and beverage industries, textile industries . It helps in the elimination of moisture from the material thus it is used in curing, drying, baking, and annealing . It is also used for the Measurement of mixed liquor suspended solids (MLSS ). In certain laboratories and hospitals, it is used to store materials at a constant temperature.

11. REFERENCES Alkadhim , Saif Aldeen Saad , Hot Air Oven for Sterilization: Definition & Working Principle (December 14, 2018). Available at SSRN: https:// ssrn.com/abstract=3340325 or http:// dx.doi.org/10.2139/ssrn.3340325 Use of Hot air oven in laboratories, prestogroup , available at https://www.prestogroup.com/blog/use-of-hot-air-oven-in-laboratories / https:// en.wikipedia.org/wiki/Hot_air_oven https:// www.isotechpl.com/blog/post/use-hot-air-oven https:// www.slideshare.net/TayyabTariq8/hot-air-oven-instrument https:// microbiologynote.com/hot-air-oven/ http ://universe84a.com/hot-air-oven / Images were taken from Google.

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