Ask Miss Science

Is my dishwasher outgassing?

I just bought a new dishwasher and it smells funny. I remember once you taught me the word "outgassing." What does that mean again? Is that what my dishwasher is doing?

You are correct!  Your dishwasher is outgassing.



In certain contexts, the term "outgassing" can have fairly specialized
meanings.  But, in this context, it is a general term used to
indicate the issuance of a gas from some substance.



Typically, the term is used when:

• the nature of the gas or the reason for its presence is unknown
  or unimportant.


• the substance releasing the gas is a solid.  That is, the
  term is usually not applied to, say, the evaporation of water from
  syrup or of solvent from a can of paint
  
  


• the presence of the gas does not necessarily imply a significant change in the nature of the substance.  For example, it is not typically used for the gases released when vegetables left sitting on the counter for a week begin to decompose, but it is used to describe the gases
  given off by carpeting and other environmental materials.
  
  


• the gases in question are released when a substance is heated or placed in a vacuum (for example, when used in manufacturing spacecraft).

The fact that you smell the dishwasher means that there is a gas coming from it: a molecule must be able to get into your nose for you to smell it.  So, unless you ground part of the dishwasher up and inserted the powder nasally, I'm assuming the molecules made it to your nose because they were gases and travelled through the air. 



The main reason that every-day objects might be outgassing is, simply put, that substances within the object are slowly drying out.  For example, consider a newly painted object.  Even after the paint is dry to touch, you can still smell it.  You can smell the paint because molecules of the thinner (aka solvent, the liquid part of the wet paint) are still escaping from the paint.  Eventually, the solvent molecules all escape and the paint no longer smells.



This is most likely what is happening with your new dishwasher.  A large part of your dishwasher is probably made of some form or other of plastic.  Some plastics are shaped by dissolving, suspending or softening them in a liquid (solvent) and then pouring them into a mold to dry into shape.  Other plastics are formed within a solvent.  Some produce a gas or liquid as they form.



It is likely that the plastic parts of your dishwasher -- and other parts that may be manufactured in similar ways -- have become dry enough to be functional, but haven't dried out completely.  In other words, you are probably smelling one or more solvents used and/or produced in the manufacture of the dishwasher.

posted by Ask Miss Science @ 8:54 PM