My work jargon includes a lot of acronyms, which sometimes causes me some internal angst when I have to write documents that include these acronyms (which is often).

How do you folks assign indefinite articles to acronyms? In English, "a" is typically used before a subject that begins with a consonant:

Example: a cat.

And "an" is typically used before a subject that begins with a vowel:

Example: an owl.

We just like having consonants separate our vowels, I suppose. But in writing, is it more important to pay attention to the letters in an acronym or the sound that is associated with pronouncing those acronyms?


For example, HEPA is an acronym for High-Efficiency Particulate Air filter. It's pronounced the way it looks: heh-pah. However, HVAC is an acronym for Heating, Ventilating and Air Conditioning systems, and it's pronounced like this: aich-vack.

So even though both of these acronyms begin with the letter "H," they're pronounced with a consonant and vowel sound, respectively. So should I write "a HEPA" and "an HVAC"? Should both of them be "a HEPA" and "a HVAC"?