What must a firm ensure for every device they install?

A firm must ensure that every device they install is laboratory certified because this certification signifies that the device has been rigorously tested according to industry standards for safety and reliability. Laboratory certification ensures compliance with regulatory requirements, which is essential for maintaining public safety and ensuring that the fire alarm system functions as intended during emergencies. Devices that are certified are proven to meet specific performance criteria, which helps reduce liability risks and enhances the effectiveness of the fire protection system.

The other options do not adequately address the crucial aspects of safety and compliance. While cost and aesthetics may play a role in the selection process, they are not the primary considerations when it comes to installing life-safety systems like fire alarms. Additionally, the notion of having a device installed for a certain period does not guarantee its effectiveness or safety, as performance can degrade over time regardless of installation duration. Hence, laboratory certification is the key requirement to ensure that the installed devices are reliable and effective in protecting lives and properties.