Presentation on hot air oven.

Hot air oven/sterilization/laboratory

1. HOT AIR OVEN Ajay Subedi Janamaitri foundation institute of health sciences,Balaju,Kathmandu

2. Introduction Electrically operated device Passing electricity through heating coils: conversion of electrical energy to heat energy Temperature is controlled by a thermostat Temperature range from 50 to 300 degree celsius .

3. Fig:Hot air oven

4. Thermostat A thermostat is a bimetallic strip .Two strip of diffferent metal of same length are fastened together,length wise,to for a thermostat. On heating,the strip bends and the temperature remains constant.

5. Principle When electricity is passed through heating coil,electrical energy is converted to heat energy.Hot air circulates in the chamber due to air convection.The oven use conduction to sterlize items by heating the outside surfaces of the items,which then absorbs the heat and moves it towards the centre of the item.The temperature is controlled by thermostat.

6. Components Double walled heavy gauge aluminium chamber. An air circulating fan: uniform distribution of the heat. 3)Thermal insulation by thick glass-wool between the working chamber and the outer mild steel casting 4)Thermostat 5)Adjustable vantilator 6)Pilot lamp 7)Temperature controller 8)Adjustable wire mesh plated trays or aluminium trays 9)Thermometer(temperature range:40 ºc to 300 ºc.)

7. Aluminium chamber pilot lamp Temperature controller Adjustable Metal shelves

8. Procedure of use Place dry articles on the shelves.(In the case of glassware,the excess water should be drained completely) Close doors firmly. Put on the main switch. Control temperature by adjusting the control knob. Keep it on for required time period.

9. 6)Put off the main switch. 7)Remove the article. Care and Maintenance Do not forget to put off the main switch when the heating perion is over. Clean the hot air oven after use.

10. working The most common time-temperature relationships for sterlization with hot air oven are:- 170 ºc for 60 minutes, 160 ºc for120minutes,and 150 ºc for 150 minutes or longer depending upon the volume.

11. Quality Control To check whether the equipment is working properly 1)Chemical control :Browne´s tubes Colour changes from red to green.

12. 2)Biological controls : paper strips containing spores of Clostridium tetani . Place strips in the oven along with other materials for the sterlization Later culture the strips in thioglycollate broth at 37 ºc for 5 days Groth in the medium indicates the failure or sterlization .  

13. Uses: Drying of glasswares / plasticwares Heating of chemicals used for the preparation of primary standards. To dry membrane/ gels in electrophoresis Chromatography procedures Other labs: Dry sterilisation. Preparation of anticoagulant vials

14. Additional information A muffle furnace is a type of hot air oven .Temperature up to 800-900 ºc can be obtained by using a muffle furnace. Specification s Following are the important specifications preferred for the selection of Hot air oven; Inner dimensions Outer dimensions

15. Number of shelves Temperature range Efficiency of thermostat,giving accuracy ±1 .  

16. references https:// www.cdc.gov/infectioncontrol/guidelines/disinfection/sterilization/other-methods.html Text book of medical laboratory technology PRAPUL B. GODKAR DARSHAN P. GODKAR

17. Thank You ☺