A fume hood sash is a glass door located at the front of the fume hood that opens and closes, serving as a doorway to the workstation. The sash is an important safety component, offering protection and containment from dangerous chemicals and other materials.
Successfully using a sash during fume hood operation involves understanding the role of the sash, the type of sash you need for your environment and safety protocols that must be in place.
Fume hoods have a fan that creates a positive air flow to pull contaminants to the filtration system. There are two types of fume hoods … ducted and ductless … and in both, the sash plays a critical role in worker safety.
Although facilities that have ductless fume hoods typically use only a few chemicals in them, the sash is nonetheless important. That’s because a fume hood sash acts as a shield. If a fire occurs, for example, the sash will contain the fire and keep it from spreading.
The sash also helps control how the air moves through the fume hood by pushing harmful vapors and fumes toward the built-in exhaust system.
While fume hood sashes slide open and closed, the direction by which they do so can vary. There are typically three types of sashes:
Vertical sashes are common in laboratory and manufacturing because they offer the greatest access to the interior of the hood. Horizontal sashes offer access to the top of the hood, but do not allow a user to easily access to both ends of the hood at the same time.
Although glass is used to construct the fume hood sash, there are several different types of glass that can be used. All are designed to absorb an explosion or fire.
When tempered glass breaks, it shatters into tiny pieces with blunt corners. It can withstand radical changes in temperature up to 392 degrees F. Compared to ordinary glass, tempered glass can withstand an impact nearly five times as strong. This makes tempered glass a popular choice for fume hood sashes.
Applications in which higher thermal resistivity is required would typically need tempered glass as the fume hood sash material. For example, tempered glass would likely be the better material if there is a routine use of equipment that emits heat or a drying oven. If there is a risk of a fire in the fume hood, tempered glass would also offer greater protection.
Laminated glass is made using two pieces of float glass. In between these two layers is a layer of polyvinyl butyral (PVB). When an explosion occurs, this sandwich approach allows the broken glass pieces to stick to the PVB layer inside, rather than falling to the ground or flying through the air.
Applications in which there is a risk for an explosion would benefit the most from laminated glass since the glass will not shatter if an explosion occurs within the hood. However, it’s important to note that tempered glass can be laminated as well, offering a higher level of protection that combines the best of both options.
If your laboratory regularly works with hydrofluoric acid, you may need a polycarbonate glass sash. Because hydrofluoric acid can damage standard glass over time, you may need to replace your sash more often. However, a polycarbonate sash is designed to protect the glass from this type of acid and give your fume hood sash a longer lifespan.
Typical applications that would use polycarbonate glass are ones in which hydrofluoric acid use is common, such as research laboratories, geology labs and facilities that perform semiconductor work.
Below are some important safety procedures to implement when using the fume hood sash:
It is important to have protocols put in place so that employees know to report any fume hood issues to a supervisor. If the fume hood is not properly functioning, an employee should close the sash and take the hood out of service.
Our article, Fume Hood Safety Steps To Take In The Event Of An Accident, further outlines what you should do if an accident occurs.
Though it may seem like a simple piece of glass, the fume hood sash is anything but ordinary.
While the fume hood itself plays an important role in keeping dangerous vapors, fumes and particles from escaping the work area, the sash allows access to the hood while protecting users from devastating injuries in the event that an accident occurs.
When used properly, the fume hood sash is a critical component of the fume hood, ensuring the safety of workers in any laboratory.