A process for producing acetic acid is disclosed in which the methyl iodide concentration is maintained in the vapor product stream formed in a flashing step. The methyl iodide concentration in the vapor product stream ranges from 24 to less than 36 wt. %, based on the weight of the vapor product stream. In addition, the acetaldehyde concentration is maintained within the range from 0.005 to 1 wt. % in the vapor product stream. The vapor product stream is distilled in a first column to obtain an acetic acid product stream comprising acetic acid and hydrogen iodide in an amount of less than or equal to 300 wppm and/or methyl iodide in an amount from 0.1 to 6 wt. %, and an overhead stream comprising methyl iodide, water and methyl acetate.