Fume hoods or exhaust hoods are pieces of laboratory furniture installed to decrease the potential inhalation exposure to biological agents and hazardous chemicals.
They must be put up and used properly to render their purpose. Know more about the many of them and how to make the most of your installation below.
Laboratory Fume Hoods: Purpose and Importance
A laboratory fume hood is a ventilated enclosure in which emitted vapors, gases, and chemical fumes are contained. They are essential for labs where the following are experimented with:
- Flammable chemicals
- Mixtures that produce a toxic aerosol
- Formaldehyde or chloroform
- Reactive substances or explosives
- Toxic gases like NO2, NH3, CO, Cl2, F2, H2S
- Odorous materials
- Chemicals with the National Fire Protection Association (NFPA) health rating of three to four
Fume Hoods Parts
Typical high-performance fume hoods or exhaust hoods have the following standard parts:
- Fume hood body
- Baffles – partitions used to create slotted openings at the back of the hood body
- Airfoil – parts that stream-line airflow into the hood
- Exhaust plenum – helps to distribute airflow evenly across the hood face
- Hood face
- Hood sash and side panels
Fume Hood Design
How a Fume Hood Works
To prevent toxic gases from being trapped inside an enclosed laboratory, fume hood components should be able to push through a process:
- The exhaust system situated on the top of the building will pull hazardous materials or toxic fumes through connected ductwork that ends in the laboratory.
- The baffles will direct the gas being exhausted.
- Then, airfoils will allow an even airflow into the fume hood by avoiding sharp curves that create turbulence.
Inner Lining Materials
The inner lining of high-performance hoods should be compatible with the chemicals they will be exposed to. Fiberglass is the most commonly used as it has good overall chemical resistance. Non-corrosive chemicals are compatible with epoxy-coated steel liners.
Another alternative is a polyvinyl chloride liner, and it is best used for laboratories that work with acids as it is corrosion-resistant. Stainless steel can also be used especially for radioisotopes and perchloric acid.
Fume Hood Performance Indicators
A typical fume hood should have a monitoring device that continuously measures air flow to provide a visible reading to the hood user. The device serves as a safety and performance indicator.
There are different types of performance indicators that can be used for fume hoods:
Magnehelic Differential Pressure Gauge
This device is mounted on the outside of the fume hood. It detects pressure through an aneroid pressure gauge. What it does is measure the difference in differential pressure between the room and the fume exhaust duct.
This is a monitoring device that is in a slightly inclined position. It can measure pressure above and below atmospheric.
Digital Monitoring Device
Since this device is digital, it works with a sensor to measure air velocity. It also has an alarm system that alerts lab users when the airflow is out of range. There is a screen that indicates the reading in color codes:
- Red – alarm mode; airflow is too high or too low
- Yellow – use with caution
- Green – safe
Fume Hood Evaluation and Maintenance
Fume hood check and maintenance should be done every year. The laboratory furniture manufacturer or supplier who installed the hoods will send a technician from their team to evaluate and record the following in a yellow tag:
- Date of inspection
- Technician’s name
- Fum hood identification or location
- Vertical sash open height or horizontal window sash opening measurement
- Approved use status (general chemistry, storage, radioisotopes, and other toxic chemicals)
- Average face velocity measurement in feet per minute (fpm)
Proper Fume Hood Techniques and Practices
Like other equipment in the laboratory, fume hoods should be cared for and handled with caution to allow them to keep serving their purpose, i.e., contain toxic gases and prevent airborne-related accidents and fire. Follow these to maintain safety when dealing with laboratory fume hoods:
- Keep the lab doors closed.
- Always keep the sash panels closed as much as possible.
- Do not remove the sash except when necessary, e.g., apparatus set-up. Make sure to replace the sash or panels before working in the hood.
- Ensure that the baffles are free of obstruction by shelving units, large equipment, or any apparatus. Keep all apparatus inside biological safety cabinets.
- Keep all apparatus at least 6 inches back from the face of the fume hood. The same goes with personnel; make sure to work away from it with the same distance.
- Do not store apparatus or chemicals in the hood as they will block the air flow. Chemical bottles in the hood must be sealed.
- If one must place something inside the hood or take something from it, do it in swift by calm manner to prevent the contained toxic fumes from escaping.
- Do not use fume hoods for waste disposal.
- All personnel who work in the fume hood should wear personal protective equipment (PPE).
- Any practice inside the lab that may generate hazardous substances at or above the Permissible Exposure Level should be done inside the hood.
- Do not put your head inside the fume hood when hazardous substances are being generated.
- As much as possible, minimize foot traffic near the hood’s face.
- Do not put electrical cords inside the hood. They may cause flammable gases and liquids to ignite.
Get the Most of Your Lab Fume Hoods’ Materials
Fume hoods are important pieces of safety lab equipment. Make sure to select the right one. Know precisely the type of work that will be performed in the room. It will help you determine the appropriate design and material.
And, once they’re installed, ensure regular safety training for all hood users in the lab for maximum protection.
We have years of experience in the manufacturing and maintenance of laboratory furniture and workstations and packaging and shipping stations. Our products come in high quality and with a warranty
Need help finding and installing the right fume hood for your lab? Get a free quote, contact us at Lab Tech Supply Co today.