Which of the following is prohibited for security personnel while on duty?

Carrying a firearm without the proper certification and licensing is specifically prohibited for security personnel while on duty because it violates legal regulations governing the use of firearms in the security field. Security personnel are typically required to have specific training, certification, and licenses to carry firearms legally. This ensures that they are knowledgeable about the laws pertaining to weapon usage, as well as understanding the responsibilities that come with carrying a firearm, including the use of force and de-escalation techniques.

Without appropriate training and licensing, not only does the individual risk legal actions if they use the weapon improperly, but they also endanger themselves and others. Therefore, compliance with firearm regulations is critical in maintaining both safety and legal standards in the security profession.

The other options involve actions that, while they may have their regulations or restrictions, do not inherently prohibit security personnel from performing them under proper guidelines. For instance, using non-lethal weapons may be allowed if properly trained, performing vehicle patrols is often a standard duty for security personnel, and identifying themselves as law enforcement can only be done under specific circumstances and regulations.