Experiments conducted in the laboratory often require highly volatile chemicals, strong acids, and bases. Chemical fume hoods have gained popularity rapidly in the industrial and research space because of their ability to properly dispose of harmful gases released during experiments. The term “fume hood” itself signifies an enclosed device that has the capability of drawing air inward with the help of mechanical ventilation.
Designing the Chemical Fume Hood
The lab fume hoods nowadays are designed concisely so that they can be installed over individual workstations. The workers can control a fume hood by simply switching it on and off. This type of lab fume hoods will keep the worker safe as they will directly draw the hazardous gaseous substances from the workstations. Another type of lab fume hood is the centralized one, often kept in the middle of the room such that it can draw air from all corners of the room.
This type of fume hood is usually bigger in size such that they can attract hazardous substances from all parts of the room. The centralized chemical fume hoods are kept running all the time. So, a lab fume hood should be chosen based on the requirements of the lab, experiments usually conducted as well as their strength. The hazardous gases collected from the working area should be channelized to places where they can be incinerated or treated properly. The objective of the fume hoods is to draw in the released poisonous gases and to dispose of them in the treatment zone properly.
Using the Chemical Fume Hood
A lab fume hood is used when working with
- Flammable or volatile chemicals like formaldehyde and chloroform
- Chemicals that come with a national fire Protection Association rating of 3 or 4
- Carcinogens and toxic gases like CO, NH3, and F2
- Explosive and reactive materials
Chemical Fume Hood Types
The fume hoods come with different types of exhaust ducts and are thus differentiated according to that. Some models of fume hoods can also operate as a ductless unit. Let’s look at the different types of exhaust duct units.
Bypass CAV Hoods:
This type of fume hood drains the same amount of gaseous substances while working. It does not matter how high or low the sash has been raised. Usually, the air velocity changes when the sash is lowered or raised at the front of the hood.
Non Bypass CAV Hoods:
The hood remains closed in the Non Bypass CAV Hoods that adds to safety. However, the drawback of the conventional CAV lab fume hood is that the forced room becomes contaminated when air pressure increases from the closed sash.
Low Flow/High-performance CAV Hoods:
In order to limit capacity, the Low/High-performance CAV Hoods contains horizontal sliding sashes sash stops. They also have newer aerodynamic designs. Even though they are quite costly, in the long run, they will make energy savings.
Variable Air Volume (VAV) Hoods:
Sash height regulates the air flow and the level is always maintained at 100 fpm. This type of fume hoods works best when the face velocity is within the range 80-120 linear feet per minute. The VAV hoods will sound alarms when malfunctions occur.
Canopy Fume Hoods:
It is akin to kitchen range hoods, and these units have a hood without enclosure or sash. It operates to remove heat, steam, non-toxic smoke, and odors.
When purchasing a lab fume hood, it is best to check out the working environment first and decide upon what type of hood will best suit it.