You will definitely take door safety to a new level with one of these door safety bars. If you're seriously concerned that somebody is going to enter your office or your home when you're there, then you can secure the door with one of these bars. Not only will the bar make the door more secure, it will also make a noise when somebody tries to open the door. A siren or a barking will sound when somebody attempts to open the door, and hopefully it will scare away any intruders. This type of unit is relatively easy to install and can definitely add to the security and safety of your home.
You can find these types of safety door bars in various styles and price ranges. These door jam bars are actually quite affordable (at amazon this model costs about $22), so if you're having a hard time sleeping at night because you fear for intrusions or break ins, then one of these products might be a good purchase.
U.S. Patrol JB5322 Alarm Security Bar
"Secures your home, dorm, office or hotel room from intruders with added security! As soon as the doorknob is touched, the alarm will sound like a powerful siren or barking dog to warn you that someone is trying to enter. An effective way to frighten away intruders. Easy no tool installation. Constructed of heavy gauge steel and uses one 9-volt battery"
This bar can be found at amazon.com