Carry a can of wasp spray.
Where I work, the handbook clearly states that no firearms are allowed on our property, not on your person, in your car, locker etc.
Many of our employees travel 45 miles to work, others have things to do or places to go to after work etc. So with that said, and knowing that at least half of our employees are CCP holders, I would bet there is a gun in 99% of the vehicles in that lot. Don't ask, don't tell, don't brag about it.
I don't know of anyone stupid enough to carry inside of the building on purpose.
One of my employees accidentally left his LCP in his pocket holster one morning and had to take it back to his truck but no one ever knew except me and him. He only told me because he knows how strongly I disagree with the policy and I'm not a snitch. And I know he has a permit.
My girlfriend works for the federal govt, she can't have a firearm anywhere near her, even in the car.