From: 8524828hau**At_Symbol_Here**COMCAST.NET
Subject: Re: [DCHAS-L] Microbiology procedures for use of Bunsen burners?
Date: August 30, 2012 11:02:29 PM EDT
Reply-To: DCHAS-L <DCHAS-L**At_Symbol_Here**MED.CORNELL.EDU>
Message-ID: <005657F5EEDE0648A9D77FFA7591B0401C19C68C**At_Symbol_Here**>

From personal experience I know that a "non-pathogenic" strain of Salmonella can cause a serious intestinal infection of an infant via a parent (who was using GOOD biohazard protection procedures)  who inadvertently transferred the organism from an undergraduate microbiology lab to the parent's home.  Similarly, some students may be immunocompromised (some because of certain medical procedures, could be susceptible to infection by organisms considered non-pathogenic for the majority of the student population. 

Professional design engineers for more hazardous microbiological research labs that are more biologically hazardous than for a typical for an undergraduate microbiology teaching laboratory strongly advocate the "good practice" of forbidding the use of a flame for sterilizing transfer loops in a microbiology laboratory.  The design engineers do so by not including natural gas piping in the laboratory design.

As mentioned by another respondent, the initial heat as the loop approaches the flame generates an aerosol of viable organisms, thus introducing inhalation as a path of exposure, and contaminating nearby surfaces.  [I learned this during a week-long training class for biosafety officers.]  The most common alternatives to flame sterilization of platinum transfer loops are (a) use disposable plastic loops, just as we use disposable pipette tips, placing the used loops in a biohazard waste container, and (b) use of a device that heats platinum transfer loops in a small bench-top furnace that contains and combusts all aerosols.  An example (not an endorsement of a specific manufacturer's device) may be visualized at

A second reason for prohibiting open flames in a microbiological laboratory is that many stains, fixatives, and solutions (e.g., 70% ethanol in water) for wiping surfaces for sterilization contain highly flammable ethanol.  A spilled container of ethanol or an ethanol-containing solution near a Bunsen burner creates an exciting event.  Depending on air currents, flash back of ethanol vapors to an open vessel (e.g. a beaker with considerable surface area) containing ethanol is most certainly a credible event. Instead of using a Bunsen burner as a heat source for other purposes (e.g., to prepare agar for growth medium), use an electric hot plate (preferably with variable heating capacity) with a magnetic stirrer. 

I agree with another respondent that ALWAYS wearing safety glasses when in a laboratory is a "first rule" of laboratory safety, whether a microbiology teaching laboratory or a chemistry teaching laboratory.   One of the deterrents to compliance with the "first rule"  is providing  uncomfortable "visitor glasses."  Many science supply companies sell much more comfortable glasses that conform with the ANSI standard for impact resistance; have a pseudo wrap-around lens design for splash-protection and better peripheral vision;  have adjustable-length, comfortable ear pieces; and cause minimal optical distortion relative to the "visitor glasses."

David Haugen

From: "Nancy A Richardson" <narichardson**At_Symbol_Here**LIBERTY.EDU>
Sent: Thursday, August 30, 2012 9:21:50 AM
Subject: [DCHAS-L] Microbiology procedures for use of Bunsen burners?

I teach in a college department that includes both biology and chemistry labs.  Our chemical hygiene plan is designed to cover both types of labs.  One statement we have is that eye protection must be worn when students use "chemicals, fire, or glass."  Lately the question has come up as to whether microbiology students sterilizing loops with a Bunsen burners need eye protection.  One thought is that professional microbiologists do not do this.  The other thought is that since we require eye protection in chemistry labs when students use the burners so we should also require it in microbiology.  Another objection is that the goggles might melt in the flame and cause another problem.  (It has been suggested we carry out tests of eye wear with burners and use tongs to hold them in the flame and determine how long melting takes.)


How have other departments handled such concerns?  Is use of burners in microbiology by students a lesser risk than use of burners in chemistry labs?


Thanks for any thoughts that anyone has on this.   --Nancy



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