Stench Chemical Log

It is imperative that researchers record their use of all malodorous substances in the Stench Chemical Log before their work begins. This will ensure that the source of any noxious odors reported in the CCB complex will be readily identified.

Examples of Stench Compounds

A few examples of stench chemicals are listed below. The use of any amount of a chemical with an overwhelmingly bad smell (e.g. thiols, selenides, sulfides) must be registered in the Stench Chemical Log. The use of common amine bases on a small scale (e.g. 1 mL of diisopropyl amine) need not be logged, however their use on a larger scale (e.g. 100 mL) should be.

• thiols (mercaptans)
• sulfides
• selenides
• amines
• phosphines
• butyric acid
• valeric acid

Running a Reaction

Extreme caution must be exercised when working with volatile, malodorous compounds. The handling of these compounds should take place inside of a fume hood to prevent the release of noxious vapors into the local laboratory environment. Precautions must also be taken to prevent these vapors from being released within the fume hood and exhausted out of the building. In addition to affecting the outside environment, these vapors can be reintroduced to the laboratory complex via building air intakes and distributed to locations that are distant from the original laboratory source.

• 1) Use the minimum amount of stench chemical possible (avoid using excess).


• 2) Perform liquid transfers by using a syringe or cannula. Never pour or pipette solutions of volatile compounds.


• 3) Keep the hood sash down as low as possible.


• 4) A cold trap or a bleach trap should be employed to prevent vapors from exhausting into the fume hood.

Bleach Traps

Thiols, sulfides, phosphines, and disulfides can be oxidized to less malodorous sulfoxides, sulfones, and phosphine oxides (or other more highly oxidized phosphorous compounds) before venting to the environment. This oxidation can be most easily accomplished using a bleach solution.

The diagram below shows the set-up for a typical bleach trap. The reaction is first vented into an empty trap, to prevent back flow, and then into a bleach solution. An excess (not a large excess) of bleach (Clorox bleach is 6.15% sodium hypochlorite by weight) should be used. The hydrochloric acid generated from the oxidation reaction is neutralized by connecting the bleach trap to a potassium hydroxide trap before venting to the fume hood. The oxidation reaction is exothermic, thus if a large amount of stench chemical is being oxidized then cooling of the traps will be necessary to keep their temperature from rising.

Solvent Evaporation

A cold-finger trap (cooled at least to -78 °C) must be used when evaporating solvent under reduced pressure when a stench chemical is present. The collection bulb must be cooled as well. Inadequate cooling of the condenser and collection flask when using the house-vacuum will result in a release of noxious vapors via the vacuum pump exhaust. If a rotary evaporator is used, it should be located inside of a fume hood.

Clean-up and Hazardous Waste Disposal

• 1) Tighten the cap of stench chemical bottles and seal them with Teflon tape.


• 2) All glassware, syringes, cannula, septa, and other labware that come into contact with malodorous compounds that can be oxidized (e.g. thiols, disulfides, phosphines, etc.) should be rinsed and/or submerged in a bleach solution to oxidize all traces of the noxious chemical. The oxidation reaction can be slow, so soaking for 24 hours may be necessary.


• 3) If disposable items such as gloves, paper towels, and septa continue to be malodorous, they should be enclosed in a zip-lock bag, placed in a wide-mouth plastic jar, labeled as hazardous waste, and placed in the hazardous waste main accumulation area for removal.


• 4) The malodorous contents of a cold-trap should be carefully added to a cooled bleach solution and the glassware rinsed and/or submerged in a bleach solution as well.


• 5) Bleach solutions should be combined into an appropriate container, labeled with a hazardous waste tag, and disposed of as hazardous waste. Potassium hydroxides solution should be added to a separate container, labeled with a hazardous waste tag, and disposed of as hazardous waste.