What do you mean by huge? Words that start with "h" that have a vowel sound in the beginning will use "an" before them. Otherwise, use "a."
an hour, an honor, an honest mistake, etc.
a hospital, a hamburger, a horrible mistake, etc.
In general, "an" comes before words that start with vowel sounds, and "a" is used before words that start with consonant sounds. Hope this helps!