Carl Clarke, director of Clarke Construction Security

1. Consider the vulnerability of the site. Various systems are available, from a simple monitored alarm with a keyholding response facility to an alarm with closed circuit television, keyholding response and a PA system.

2. The system should: know when it is being attacked and send an alert; remain functional for a period if power is lost; include a radio link. CCTV should have on-site digital recording, a colour monitor, and provide a log of events, time and date.

3. Suppliers should be able to provide: a turnkey solution including installation, monitoring and response; access controls that integrate with the security system, if required; and a 24/7 emergency engineer call-out service.

4. Use a reputable supplier with Security Systems and Alarms Inspection Board accreditation or similar, and which employs full-time engineers with Criminal Records Bureau clearance. The firm should be insured and ISO9000 certified.

5. Consider your long-term security needs. Systems are available for hire or for purchase. If you only plan to be in a place for a certain period, renting equipment could be more cost effective.