CO₂ fire extinguishing

The banning of halons has revitalised the use of carbon dioxide extinguishing systems. CO₂ fire-extinguishing systems are considered clean agent systems because their use ensures quick and clean extinguishing, without releasing any residue into the area where the agent is dispensed and allowing rapid resumption of activities after use.

The extinguishing action of CO₂ is based on reducing the concentration of oxygen in the air to a level at which combustion cannot be sustained; the simultaneous cooling caused is a secondary effect in extinguishing fires.

The restriction on their use is due to the hazardous nature of CO₂ which, by lowering the concentration of oxygen, makes the air unbreathable and can, therefore, be dangerous for human beings: at the national level, the adoption of these systems is essentially limited to environments that are not normally occupied by people.

Carbon dioxide is stored in cylinders and/or tanks in liquid form and is then dispensed into the environment through special nozzles in vaporised form. The systems can be completed with suitable fire detection systems, timers, and control panels for automatic operation.

In order to ensure their effectiveness, it is essential that the checks required by the standards, which detail all the activities and maintenance schedules, be performed by specialised personnel.

Maintenance phases and frequency

Documentation to be acquired prior to starting maintenance activities

• User and maintenance manual;
• As-built designs and documentation of the system;
• Manufacturers' test procedure;
• Test equipment;
• Electronic instruments suitable for the tests to be performed.

Initial inspection

To be performed by the Maintenance Technician

Preliminary Inspection

• Verification that the system corresponds to the executive plan; Installation in conformity with the standard;
• Visual inspection of the system;
• Checking the cylinders and related calculations.

Functional Check

• Verification that the system logics correspond to the project requirements and the operating documents as well as the user and maintenance manual;
• In the presence of other interconnected systems (active or passive protection or technological systems), check that the system logics are consistent with the project requirements.

Monitoring

To be completed by the Assigned personnel

What?

• Visual inspection;
• Checking the status messages on the control unit;
• Checking the condition of cylinders, nozzles, goosenecks, etc., at least monthly.

When?

• Daily, weekly, monthly depending on the type of check to be carried out and the size of the system.

Increase frequency in the case of:

• Installations in environments with a high density of personnel;
• Installations in environments with frequent temperature changes;
• Installations in environments with high humidity or presence of vapours;
• Specific requirements of the manufacturer or designer.

Periodic inspection

To be performed by the Maintenance Technician

What?

• Check that the initial inspection documents are on hand;
• Check that no actions have been taken or structural changes made in the protected environment;
• Verification of the state of the system.

How?

Conventional systems:

-

100% testing of devices

Analogue Systems:

0-6 years

Over a period of 12 months a functional check must be performed on 50% of all devices in all detection zones (twice per year)

7-12 years

Over a period of 12 months a functional check must be performed on 100% of all devices (twice per year)

beyond 12 years

After 12 years the system must undergo a general review

General system check

To be performed by the Maintenance Technician

When?

• At least once every 12 years.

What?

• Verification of the availability of spare parts;
• Verification that the system has not changed (if substantial modifications have been made, the technical documentation must be acquired in the new as-built configuration).

How?

• Factory overhaul;
• Replacement with new detectors;
• Execution of physical test.