Does your business spend more time in the backroom filling orders or working on manufacturing than it does dealing with customers onsite? If so, chances are you don't have a single customer entrance that is monitored by an employee. In this case, you need to make sure your entrance while still keeping your premises safe and secure. The following options can help you with this goal.
Option #1: Entry Systems
Install an entry system on each exterior door. These systems open easily from the inside, so exiting is not an issue, but they require a code or card swipe on the outside to disengage the lock. Card systems work well, since an entrance card can also double as an employee badge. If you are worried about lost or forgotten keys, you can use a keypad system. Assign each employee their own personal entrance code. This way you can track usage or disable a code when someone quits.
Option #2: Restriction options
A restricted system can be used both externally or internally. The most common external restriction is to not allow certain codes or cards to activate the locks after hours. This way you don't have to worry about someone breaking in at night, such as if a thief finds a lost key card. Internal systems work well if you have areas that are off limits to certain employees for safety or security reasons.
Option #3: Paging stations
Even if you don't have a customer office on site, you may still get visitors or vendors from time to time. A paging station can solve this dilemma. Place the station as the most obvious door, but then make sure there are signs at all other entrances directing visitors to the station. This station can be as simple as a doorbell, but for security purposes you may want to have a speaker system installed, or even a speaker and video system. Make sure chimes or speakers are installed throughout your building so they will be heard when a visitor is present.
Option #4: Safety hardware
Finally, install some safety hardware on your doors. Door closers ensure that doors close after use and don't get stuck in an open position. If you move heavy or awkward items out of your shop, you may want to install continuous hinges so the door can swing both ways. Another option can be lockdown or panic hardware. These are used to seal and bolt a door closed, such as in the event of an attempted forced entry.
Contact a commercial locksmith (such as one from http://www.suburbanlock.com) to further explore your options.