Safety cabinet
A safety cabinet is a sterile workbench that is used in cell culture laboratories or when working with sensitive materials, such as B. semiconductor materials in semiconductor technology , application. A safety workbench consists of a work table with a housing that is specially ventilated. A distinction is made between the microbiological safety workbench and the clean room workbench . Both safety workbenches, with the exception of the class I microbiological safety workbench, initially protect the product by introducing filtered air. The clean room workbench (product protection workbench, English laminar flow cabinet ) offers the user no protection. The microbiological workbench ( biosafety cabinet (BSC) or microbiological safety cabinet) also protects the user against the escape of (contaminated or potentially contaminated) microorganisms and aerosols .
Cleanroom workbench
A clean room workbench (also known as product protection workbench or vaccination bench; English laminar flow cabinet , flow for short ) is only used for product protection. The exhaust air is not specially filtered and blown into the work area, so that the user is unprotected. Due to the simple design, the clean room workbench is cheaper than the microbiological sterile workbench. However, it is not suitable for microbiological and biotechnological work. The clean room workbench is used for sterile work without microorganisms, i.e. for the filtration of media or buffers and when working with sensitive materials such as semiconductor materials or microelectronics. Depending on the air flow, a distinction is made between
- Clean room workbench with horizontal air flow and
- Clean room workbench with vertical air flow.
In both cases, the pre-filtered room air is cleaned by a particulate filter. With horizontal air flow, this filter is located on the rear wall of the workbench. The air is conveyed horizontally to the front and blows unfiltered towards the user into the work area. The vertical air flow can be directed from bottom to top or from top to bottom.
Microbiological workbench
In contrast to the clean room workbench, the microbiological safety workbench not only protects the product, but also the user from microorganisms and aerosols. In English, the microbiological safety cabinet is known as the biosafety cabinet (BSC) or microbiological safety cabinet . There are microbiological safety workbenches with different safety levels :
- Class I - worker protection
- Class II - protection of workers and the subject of work
- Class III - increased protection of workers, protection of the subject of work
function
In order to prevent airborne organisms, spores or aerosols from escaping, air is sucked out of the interior of the safety workbench through a particulate filter. Part of the extracted air is blown back into the work area along the front (open for work). For this purpose, a powerful ventilation system is installed above the work area.
In class I microbiological safety workbenches , room air is sucked through the work opening over the work surface. Aerosols and particles are carried to a filter. Employees are protected as long as the air flow is not obstructed. Arms and hands that are in the housing are unprotected. There is no product protection. Class I microbiological safety cabinets are mostly used to store devices that may generate aerosols (e.g. centrifuges).
In class II microbiological safety workbenches ( Laminar Air Flow Box ), part of the filtered exhaust air is blown downwards in a laminar flow as an "air curtain" along the partially open front window and fed back to the filter together with the room air drawn in so that the Fresh air is cleaned before it comes into contact with the work material. At the same time, this minimizes the risk that particles from inside the workbench (safety chamber) can get into the laboratory environment through the partially open front window. Sensors trigger an alarm if the laminar flow is so severely disturbed that the inside and outside air are mixed by vortices . This can happen if the front window is opened too far. Another possible cause is the storage of too many items within the safety cabinet. These objects can negatively affect the airflow.
Class III microbiological safety workbenches ( glove box ) are completely closed. They have built-in gloves and locks through which tools and work materials are brought in. Both supply air and exhaust air are passed through a particulate filter, with a negative pressure being maintained inside , so that no potentially contaminated indoor air escapes in the event of leaks. These safety cabinets are listed in the EU as dual-use devices and may be subject to export restrictions .
Regulations
Safety workbenches serve to protect the working person (as well as the work item). There are various standards that a safety cabinet should comply with. Class II and III microbiological safety workbenches correspond to DIN EN 12469 and are therefore suitable for microbiological and biotechnological work. In the USA this is regulated by NSF49. A certification by an independent testing laboratory is recommended. After the safety cabinet has been set up in the laboratory, an acceptance test by a certified body is recommended. The WHO recommends a maximum period of use of 15 years.
Other equipment
The interiors of safety workbenches are modularly designed from stainless steel or other suitable materials so that the work surface can be removed in order to clean it and the space below. Often there are suction devices for liquids, sockets and gas connections inside the safety workbench. Safety workbenches can be equipped with UV lamps to sterilize the interior . These must remain switched off when working in them, as they can quickly lead to skin damage ( sunburn ). They would also damage or kill the cells being worked with. The front of safety workbenches is equipped with a glass pane that can be completely closed. This front window is moved manually in older devices, in modern devices this is done electrically via a motor . The front window shuts down when not being used, especially when sterilizing with ultraviolet light.
ergonomics
Safety workbenches are mostly used daily and tw. used for several hours. In addition to the protection of the working person and the sample material, the aspect of ergonomic working is becoming increasingly important. This includes the lowest possible noise pollution from the ventilation system , a height-adjustable work surface and strong but glare-free light sources.
maintenance
Safety cabinets require regular maintenance. This checks whether the air flow complies with the regulations, i.e. the safety of the working person and, if necessary, the sample material. The particulate filters have a limited service life. Depending on the purity of the laboratory air and the purity of the samples, the permeability of the filters is reduced over time. Modern safety workbenches measure the filter air flow. If this is too low, an alarm will sound. The filters should only be replaced by competent persons, as the filters are to be regarded as potentially infectious material. If a UV lamp is used, it should also be replaced after a certain period of time, depending on the daily usage time. The radiation output of a UV lamp decreases over time, so that a complete sterilization of the work surface u. U. is no longer guaranteed.
Installation in the laboratory
In contrast to other laboratory equipment ( pipette , centrifuge , thermal cycler ), safety workbenches are very large (approx. 2.40 m high, 80 cm deep, up to 2 m long) and heavy (up to 350 kg). A precise measurement of the laboratory, in most cases the cell culture laboratory , and, if necessary, checking the load-bearing capacity of ceilings and elevators as well as the corridors and doors between the building entrance and the planned location of the safety cabinet are required. The positioning of the safety workbench within a laboratory depends on the position of the doors and the ventilation system. The workplace at a safety workbench should have as little external air turbulence as possible.
Demarcation
Safety cabinets are sometimes confused with fume cupboards . In contrast to fume cupboards, however, safety workbenches only provide protection against particles and aerosols . Gases and vapors are not retained in their filters.
Safety workbenches are also used for non-biotechnical work under clean room conditions , for example in semiconductor production.
A glove box is used to work with the material to be treated as completely closed as possible, usually in a special atmosphere.
Web links
Individual evidence
- ↑ genetic engineering. Retrieved April 13, 2017 .
- ↑ Schmitz, Sabine .: The experimenter: cell culture. Springer, 2012, ISBN 978-3-8274-2572-0 .