When you sneeze, hundreds of thousands of germ particles disperse through the air. These little germs will attach themselves to anything they land on, including dust, but some germs will continue to float around in the air over many days. Contamination in the laboratory will occur when particles that float around land in open tubes and dishes. Without proper air flow, it is difficult to protect specimens from contamination.
A flow hood can control air distribution within an enclosed area to provide clean working space to scientists. There are many different types of flow hoods, so alaminar flow hoodis only one type. Laminar flow hoods move air in straight layers through a filter. The straight layers are arranged at specific speeds that prevent the air layers from mixing before filtering. Filters used in laminar flow hoods are constructed to provide high-efficiency particle arrestance (HEPA). These filters capture particles better than regular filters used in other applications. Though some laminar air hoods have additional disinfectant capabilities most typical HEPA filters only remove most, if not all, contaminant particles from the air. Laminar air filters should be replaced occasionally because constriction will need to be avoided. Processed air will be pushed by a blower towards the outside of the air flow hood to prevent contaminated air from entering the work area. Blowers should be monitored regularly to detect any congestion or irregularities. Different types of laminar air flow hoods will provide various levels of security.
Air Flow Direction
- Horizontal air hoods will take in air from the outer environment, filter the air, and blow the clean air from the back of the air hood towards the user. These laminar air hoods protect the specimen more than the scientist and should not be used with hazardous or infectious samples. Horizontal air hoods do not have glass screens because they would block the horizontal air flow, so there is no splash protection either.
- Vertical air hoods take air from both the outside environment and used air from the internal environment to provide air to the workspace. Air is filtered and blown over the work area from the top in a downward direction. This direction of air flow protects both the worker and the products because air can be completely circulated within the closed environment. With some types of vertical air hoods, the user never has to come in contact with the air from the inside of the laminar hood. These air hoods have glass screens that provide an extra layer of protection between from the outside to the inside. Some of the glass screens are air tight with only holes where a person can insert arms into the workspace.
- Class I laminar air flow hood is a simple design that provides mostly clean air, but it does not disinfect and lacks advanced filtering abilities. As a fume hood in a chemical laboratory setting, it works very well. This type of fume hood is not to be used with infectious or hazardous substances.
- Class II hoods provide more adept air filtering abilities. Plus, some of these will disinfect the work area. This class is suitable to be used with hazardous materials. However, do not use a Class II with human pathogens.
- Class III provides the most protection against air contamination. This class will thoroughly filter and disinfect air. Air cleaning mechanisms of this type of laminar hood make it suitable with experiments of human pathogens, infectious substances, hazardous materials, and general use. Typically, this is the most expensive type of laminar air hood, but it will provide the greatest protection and can be used across many applications.
Optional Disinfecting UV Lamps
There are air hoods that have an additional method of protection that does not involve air. Disinfecting UV lamps will stay on when the hood is not being used to prevent the growth of pathogens and keep the workspace as disinfected as possible. These additional lamps should not be left on during use because the UV rays can cause significant health problems to the worker, but they are useful in keeping a work area in optimal conditions during downtime.
Consider this information when deciding which laminar air flow hood to put in a laboratory.