Steam boiler dirty sight glass

[Mike Lamb]

Does a dirty/opaque sight glass mean a steam boiler has not been flushed regularly? 

[Bill Kibbel]

It could be, or the boiler has been drained and refilled or skimmed recently and they didn't bother to clean the glass.  Dirty glass is usually way, way down the list of all the crap wrong with a majority of steam boiler installations.