Red light/Green Light In Aseptic Technique: When Is The Flame OK?

My mom is a microbiologist and so I was a lot more informed about bugs than most kids. In fact, I probably gave more than one classmate nightmares with my talk of there being 10 times more bacteria that make up the human body than human cells.

I remember my mom working by a Bunsen, flaming her wire loop and bottlenecks and always being careful to stay near the flame.

But how does this faithful, long-loved lab tool work? In a nutshell it does two things:

• Firstly, it creates an updraft of heated air helping to sterilize the air around it
• Secondly, it can be used to kill bugs directly when you “flame” equipment over it

So no procedure in microbiology should get the green light as being bug-free without the blue light of a Bunsen, right? Or are there times when you should red light the sacred flame? There are indeed!

Good aseptic technique is often accompanied by some healthy paranoia (DON’T TOUCH MY BUGS WITH YOUR BUGGY HANDS!) but there are times when you need to quench your burning desire (pardon the pun) to turn on that Bunsen.

Let’s shine a light on when a Bunsen is a no-no and a go-go.

Red light

1. Stay put or turn it off! Do not use a flame if you’re planning on leaving the lab. I put this as number one because of the seriousness of neglecting this rule. You may only be nipping out for a quick call but it’s just not worth it. Something could catch fire or a draft could put out the flame leading to gas leaking everywhere. This brings me to point 2.
2. Never use a Bunsen next to a window or draft!
3. Do not flame anything plastic. Instead, take care not to touch pipette tips on the sides.
4. Do not use a Bunsen to flame a container full of anything flammable!
5. Do not use a Bunsen on the orange flame. This flame is not enriched with oxygen and thus burns at a lower temperature. Also, when flaming things, put the object just above the flame where it’s hottest.
6. When pouring agar plates, it is better to do so in a hood rather than next to the Bunsen. The air by the Bunsen is not completely sterile and drafts from doors opening or people walking past will disturb its field of effectiveness.
7. Do not work more than a few inches from the flame. Our friend the trusty Bunsen can’t help sterilize air that is on the other end of your desk!
8. If you are working with bugs that may release spores, a Bunsen is not effective enough. A hood is an absolute must.

Green light

1. When streaking plates with a metal loop.  Use a Bunsen to flame your loop after every pick.
2. Use the Bunsen to flame the necks of glass bottles and tubes when picking colonies into liquid media.
3. Also flame bottle necks when transferring solutions between containers.
4. Use the flame to sterilize instruments (e.g. forceps) quickly.

There you have it!

Aseptic technique can be tedious to learn but there is a light at the end of the tunnel!

When would you red light the flame? Any horror stories you’d like to share?