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Module 3 Use, calibration and maintenance of laboratory equipment. Learning objectives. At the end of this module you will be able to: describe briefly the operating characteristics of biological safety cabinets, centrifuges, autoclaves, inspissators, pH meters, incubators;
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At the end of this module you will be able to:
Principles, use and maintenance of:
A ventilated contained area providing
protection for the operator and the
environment against infectious aerosols
during the handling of hazardous microorganisms
The most important equipment in all diagnostic mycobacteriology laboratories is the BSC.
HEPA = high-efficiency particulate air
The HEPA filter traps and remove 99.97% of airborne particles of diameter 0.3 µm or more.
BSC class I and II – main differences
Class IIB BSC
Class IIA BSC
A,B– not recommended
Never work with the UV lamp on.
Do not use corrosive substances.
Regular certification and maintenance, with replacement of filters, are needed and represent a major challenge in low-income countries. If maintenance is not carried out regularly, the filters may become clogged and tubercle bacilli may be blown into the face of the operator. A BSC that is not well maintained is more hazardous than protective.
Performance of the BSC should be evaluated by the manufacturer or a qualified professional, with specific, well-calibrated equipment.
The BSC should not be used until this maintenance has been carried out.
Airflow smoke pattern tests are performed to determine:
A cabinet leak test is carried out:
Fumigation of the BSC should be carried out:
RCF (or g) = relative centrifugal force
rpm = revolutions per minute
RCF = 1.12 * 10−6 *r *v2
RCF (g) = 1118 x r x (v/1000)2
r = radius in mm
v = speed in rpm
rpm = 1000 *√RCF/1.12 *r
Always work in RCF, not rpm: new
centrifuges can convert automatically.
Annual service should be carried out by a qualified service technician: centrifuge brushes, timer, speed and electrical leaks should all be checked.
The autoclave using saturated steam under pressure is the most efficient means of:
For optimum function:
Separate autoclaves should be used for sterilization of solutions or glassware (clean materials) and for decontamination of infectious materials.
Pressure-cooker laboratory autoclave
Autoclave with air discharge by gravity displacement
*pH 10 can be used if commercially purchased
Incubators ensure optimum growth conditions for culture of M. tuberculosis.
Incubators are available in various sizes, from small (benchtop) models to large closets up to several hundred liters. Walk-in incubator rooms with circulating fans to obtain an homogeneous temperature are also frequently used.