Books
He always entered via the ventilation system rather than the main lobby because the main lobby was patrolled by robots whose job it was to quiz incoming employees about their expense accounts.
— Douglas Adams · Mostly Harmless

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
A comic bit of office absurdity: he sneaks in through the vents to dodge lobby robots whose job is grilling arrivals about their expenses. The joke is how petty and bureaucratic the guard duty is, and how far he'll go to avoid it.
Context reviewed