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Hot Air Oven

Hot Air Oven

Hot Air Oven: commonly used for dry heat sterilization. It employs higher temperatures in the range of Hot Air Oven160-180°C and requires exposures time up to 2 hour, depending upon the temperature employed. The benefit of dry heat includes good penetrability and non-corrosive nature.

Hot Air Oven, which is usually used for the dry heat sterilization is consists of the following parts:

  • An insulated chamber surrounded by an outer case containing electric heaters.
  • A fan
  • Shelves
  • Thermocouples
  • Temperature sensor
  • Door locking controls

How to Operate a Hot Air Oven?

  • Articles to be sterilized are first wrapped or enclosed in containers of cardboard, paper or aluminum.
  • Then, the materials are arranged to ensure uninterrupted air flow.
  • Oven may be pre-heated for materials with poor heat conductivity.
  • The temperature is allowed to fall to 40°C, prior to removal of sterilized material.
  • Laminar Flows
  • Laminar air flows can maintain a working area devoid of contaminants. Many medical and research laboratories require sterile working environments in order to carry out specialised work. Laminar Flow Cabinets can provide the solution
  • How They Work
  • The process of laminar air flow can be described as airflow where an entire body of air flows with steady, uniform velocity.
  • Laminar Flow Cabinets work by the use of in-flow laminar air drawn through one or more HEPA filters, designed to create a particle-free working environment and provide product protection. Air is taken through a filtration system and then exhausted across the work surface as part of the laminar flows process.
  • Commonly, the filtration system comprises of a pre-filter and a HEPA filter. The Laminar Flow Cabinet is enclosed on the sides and constant positive air pressure is maintained to prevent the intrusion of contaminated room air.

Types of Laminar Flow Cabinets

Laminar Flow Cabinets can be produced as both horizontal and vertical cabinets. There are many different types of cabinets with a variety of airflow patterns for different purposes.

  • Vertical Laminar Flow Cabinets
  • Horizontal Laminar Flow Cabinets
  • Laminar Flow Cabinets and Hoods
  • Laminar Flow Benches and Booths

All ensure a work space devoid of contaminants and may be tailored to the lab requirements.

Autoclave An autoclave is a pressure chamber used to carry out industrial processes requiring elevated temperature and pressure different from ambient air pressure. Autoclaves are used in medical applications to perform sterilization and in the chemical industry to cure coatings and vulcanize rubber and for hydrothermal synthesis. They are also used in industrial applications, especially regarding composites

Air Removal

It is very important to ensure that all of the trapped air is removed from the autoclave before activation, as trapped air is a very poor medium for achieving sterility. Steam at 134 °C can achieve in three minutes the same sterility that hot air at 160 °C can take two hours to achieve. Methods of air removal include:

Downward displacement (or gravity-type): As steam enters the chamber, it fills the upper areas first as it is less dense than air. This process compresses the air to the bottom, forcing it out through a drain which often contains a temperature sensor. Only when air evacuation is complete does the discharge stop. Flow is usually controlled by a steam trap or a solenoid valve, but bleed holes are sometimes used, often in conjunction with a solenoid valve. As the steam and air mix, it is also possible to force out the mixture from locations in the chamber other than the bottom.

Steam pulsing: air dilution by using a series of steam pulses, in which the chamber is alternately pressurized and then depressurized to near atmospheric pressure.

Vacuum pumps: a vacuum pump sucks air or air/steam mixtures from the chamber.

Superatmospheric cycles: achieved with a vacuum pump. It starts with a vacuum followed by a steam pulse followed by a vacuum followed by a steam pulse. The number of pulses depends on the particular autoclave and cycle chosen.

Subatmospheric cycles: similar to the superatmospheric cycles, but chamber pressure never exceeds atmospheric pressure until they pressurize up to the sterilizing temperature.

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