Use engineering controls.

·         Use chemical fume hoods and other engineering controls as needed.

Vacuum Trapping

When using a vacuum source, it is important to place a trap between the experimental apparatus and the vacuum source.  The vacuum trap

·         protects the pump and the piping from the potentially damaging effects of the material

·         protects people who must work on the vacuum lines or system, and

·         prevents vapors and related odors from being emitted back into the laboratory or system exhaust.

There have been incidents at UC San Diego where improper trapping caused serious failure of building vacuum pumps and in one case in 2009 the explosion was so severe that the pump was completely destroyed leaving the vacuum system in disrepair for months. Luckily no one was injured.  

Proper Trapping Techniques 
To prevent contamination, all lines leading from experimental apparatus to the vacuum source should be equipped with filtration or other trapping as appropriate. 
 

·         For particulates, use filtration capable of efficiently trapping the particles in the size range being generated

·         For most aqueous or non-volatile liquids, a filter flask at room temperature is adequate to prevent liquids from getting to the vacuum source.

·         For solvents and other volatile liquids, use a cold trap of sufficient size and cold enough to condense vapors generated, followed by a filter flask capable of collecting fluid that could be aspirated out of the cold trap.

·         For highly reactive, corrosive or toxic gases, use a sorbent canister or scrubbing device capable of trapping the gas.

Cold Traps 
For most volatile liquids, a cold trap using a slush of dry ice and either isopropanol or ethanol is sufficient (to -78 deg. C).  Avoid using acetone.  Ethanol and isopropanol 
are cheaper and less likely to foam.

Liquid nitrogen may only be used with sealed or evacuated equipment, and then only with extreme caution.  If the system is opened while the cooling bath is still in contact 
with the trap, oxygen may condense from the atmosphere and react vigorously with any organic material present.