What are the features of Classic Carbon monoxide alarm?

Here are some general characteristics of a classic carbon monoxide (CO) alarm:
Detection: A CO alarm is designed to detect the presence of carbon monoxide gas in the air. It does this by measuring the level of CO in the surrounding environment and sounding an alarm if it reaches a dangerous level.
Power source: CO alarms can be powered by batteries or by being plugged into an electrical outlet. Classic CO alarms often use replaceable batteries, although some models may have a built-in, non-removable battery that needs to be recharged periodically.
Loud alarm: A classic CO alarm typically emits a loud, high-pitched sound when it detects dangerous levels of carbon monoxide. The volume and pitch of the alarm may be adjustable, depending on the specific model.

Test button: Most CO alarms have a test button that allows you to check that the alarm is working properly. Pressing the button will simulate a CO gas detection and cause the alarm to sound.
Digital display: Some CO alarms have a digital display that shows the current level of carbon monoxide in parts per million (ppm). This can help you to monitor the CO levels in your home or office and take action if necessary.
Certification: CO alarms may be certified by a recognized testing agency such as UL (Underwriters Laboratories) or CSA (Canadian Standards Association) to meet certain safety standards.
Overall, the characteristics of a classic carbon monoxide alarm would make it a reliable and effective way to detect dangerous levels of CO gas in your home or workplace. By sounding an alarm when CO levels are high, these alarms can help to protect you and your family or coworkers from the potentially harmful effects of carbon monoxide poisoning.