Ductless Fume Hood Case Study: Xylene Fumes

Xylene Fumes:

Xylene is a name given to any one of three aromatic hydrocarbon isomers produced from crude oil. Each of the isomers is similar in its properties. There are many applications in which the use of these xylene isomers is necessary including uses such as a solvent in the leather, rubber, and printing industries. It is often used as a blending agent in gasoline or as chemical intermediate in the production of various plastics, medicines and dyes. Xylene is also used in smaller scale lab operations such as in the semiconductor industry because it is a good cleaning agent for silicon wafers. Additionally, it is used as a sterilizer. When xylene is applied in these situations, its vapors or fumes can become an irritant to the user; therefore, an effective method of removing these fumes, such as a ductless fume hood, is necessary. Xylene vapors are toxic and extended exposure to them can lead to problems in the respiratory tract. Furthermore, the vapors are very flammable. Consequently, adequate controls must be used to prevent prolonged exposure. The variety of ductless fume hoods offered by Sentry Air Systems will help prevent exposure to these chemicals.

Recently in fact, an in-house efficiency test confirmed the ability of the Sentry Air Systems activated carbon filter cartridge to remove chemical or organic vapors from the air stream within a ductless containment hood. For the test a 99% solution of O-xylene was placed in an open container inside the SS-324-DCH. In order to determine how well the xylene vapors were absorbed, sampling pumps were used to measure the concentration of the xylene at four specific locations: within the Sentry Air System 24″ ductless containment hood, on the outlet of the ductless fume hood, on the operator standing in front of the ductless fume hood, and a spot in the room on the opposite end of the ductless fume hood. An independent lab verified the measurements of the xylene vapor concentration. A second test was performed as a control to compare the xylene vapor concentration in the room without the ductless containment hood running.

The test parameters included the following:

1) Sentry Air Systems Model SS-324-DCH ductless containment hood was set up with a 10 lb Carbon filter. The 300 series unit with carbon filter generates sufficient air volume to keep the air velocity at the hood inlet greater than 100 FPM.

2) 125 mL of o-xylene was placed within the ductless fume hood. The ductless fume hood was turned on and the air was sampled at the respective locations for 25 minutes while the ductless fume hood was running.

3) The control test also used 125 ml of o-xylene under the SS-324-DCH ductless containmenthood. The two sampling pumps were also turned on but the ductless fume hood wasn’t.

Efficiency of Sentry Air Systems ductless fume hoods on xylene:

The samples were analyzed by the independent HIH Laboratory and the results were reported in the following table:


The results from the independent lab show that the xylene vapors were removed from the airstream within the ductless fume hood with a 99% efficiency. The control shows that the filter basically eliminated any exposure that the operator had to the xylene vapor during a 25 min period. The exposure level while the ductless containment hood was running is at least 3x less than what it was during the control experiment. It most certainly is much lower than that but the lower limit of detection was reached so it is impossible to say what the exact level of efficiency achieved is with confidence. Had the test been significantly extended, it is likely that the operator would have been exposed to much greater than 1.5 ppm of xylene vapor, whereas, the hood and filter would have prevented this exposure. Under the conditions present during this testing, the Sentry Air Systems ductless hood is capable of creating a NIOSH compliant working environment for the operator and eliminating 99% of xylene vapors from the air stream.