a/an

[Peter Neilson]

Yes, as commonly pronounced.

Some make a further rule for words beginning with H:

If the accent is on the first syllable (a humid day), it's "A". If 
elsewhere (an humidifier) it's "AN".

The question on whether to adopt this rule revolves around how one 
pronounces the H. Those who tend towards "youmidifier" will tend to 
choose "an" and those who distinctly say "HHHumidifier" might prefer 
"a". Those who call H "a haitch" instead of "an aitch" should absolutely 
say "a" before H. But I'd be reluctant to hire them as tech writers.

If you are documenting humidifiers, avoid the dispute by avoiding the 
indefinite article, and say, "your humidifier" or "the humidifier".