Mechanical Smoke Ventilation Servicing, Testing and Competence

Mechanical smoke ventilation systems are life-safety systems. They need to work during a fire, including in conditions where parts of the building's normal services may already have failed.

Unlike a conventional fire alarm system, a mechanical smoke control system can bring several different engineering disciplines together within one installation.

A typical system may include:

• fire alarm interfaces;
• smoke control panels and PLCs;
• motorised smoke dampers;
• automatic opening vents;
• three-phase extract and supply fans;
• duty and standby fan arrangements;
• variable speed drives and soft starters;
• motor protection and contactors;
• automatic transfer switches;
• normal and secondary electrical supplies;
• generators, UPS systems or other standby supplies;
• pressure and airflow sensors;
• manual firefighter controls;
• smoke shafts and ductwork.

Because of this, maintaining a mechanical smoke ventilation system involves considerably more than checking that a fire alarm output causes a fan to start.

BS 7346-8 covers the planning, design, installation, commissioning and maintenance of smoke control systems. Its scope includes mechanical smoke ventilation, along with the associated controls, power supplies and interconnections.

A proper maintenance regime therefore needs to consider the system as a whole.

Legal and Standards Framework

Regulatory Reform (Fire Safety) Order 2005

For premises within scope of the Regulatory Reform (Fire Safety) Order 2005, Article 17 requires relevant fire precautions to be maintained in an efficient state, in efficient working order and in good repair.

For a mechanical smoke control system, this should not be taken to mean only the fire alarm interface.

The fans, dampers, controls, power supplies and other equipment needed for the system to operate form part of the overall life-safety arrangement.

BS 7346-8:2013

BS 7346-8:2013 is the main UK code of practice covering the planning, design, installation, commissioning and maintenance of smoke control systems.

Its scope includes:

• natural smoke ventilation;
• mechanical smoke ventilation;
• smoke barriers;
• smoke and heat exhaust ducts;
• smoke dampers;
• controls;
• power supplies;
• interconnections.

The standard remains current at the time of writing.

BS EN 12101-10

BS EN 12101-10 covers power supplies for smoke and heat control systems, including primary and secondary electrical and pneumatic supplies.

The condition and reliability of the power supply should therefore be treated as part of the smoke control system, not as an unrelated building-services item.

Electricity at Work Regulations 1989

Where servicing or testing involves electrical equipment, the Electricity at Work Regulations 1989 apply.

Regulation 16 requires people carrying out work where technical knowledge or experience is needed to prevent danger or injury to possess that knowledge or experience, or to work under suitable supervision.

Competence is task-specific.

Being competent to service a fire alarm system does not automatically make someone competent to test three-phase motors, open an ATS, work on a VSD or carry out live electrical measurements.

Where work is carried out on or near exposed live conductors, Regulation 14 also becomes relevant.

Electrical testing and fault finding are examples of work where energised conditions may sometimes be necessary, but this does not remove the need for justification, suitable precautions and competent persons.

PUWER

The Provision and Use of Work Equipment Regulations 1998 may also apply to smoke control machinery and associated equipment.

PUWER covers maintenance, inspection, training and isolation from energy sources.

Mechanical smoke ventilation equipment can contain several forms of hazardous energy, including:

• electrical energy;
• rotating machinery;
• stored mechanical energy;
• automatic movement;
• pneumatic equipment in some systems.

Safe isolation may therefore involve more than simply switching off an electrical supply.

Competence Is Task-Specific

Mechanical smoke ventilation sits across several engineering disciplines.

One engineer does not necessarily need to be competent in every discipline involved, but the people carrying out the work collectively need to be competent for the work being undertaken.

Fire Detection and Alarm Competence

This may include:

• testing fire alarm initiation;
• verifying interface outputs;
• testing monitored inputs;
• checking alarm transmission to the smoke control system;
• confirming the correct fire alarm cause and effect.

A competent fire alarm engineer may be entirely suitable for this part of the work.

Smoke Control Competence

This may include:

• understanding the smoke control strategy;
• interpreting cause and effect;
• testing sequential operation;
• checking smoke damper operation;
• testing duty and standby arrangements;
• understanding pressure relationships;
• testing manual overrides;
• understanding system failure modes;
• assessing airflow and system performance.

This requires knowledge specific to smoke control.

Electrical Competence

Mechanical smoke control systems frequently contain equipment such as:

• 230 V and 400 V supplies;
• three-phase motors;
• automatic transfer switches;
• contactors;
• MCCBs;
• motor protection;
• variable speed drives;
• generators;
• secondary supplies.

Testing or fault finding on this equipment can require electrical competence quite separate from fire alarm or smoke control competence.

Mechanical Competence

Fans, dampers and associated plant also create mechanical hazards.

This can include:

• rotating fan impellers;
• belts and couplings;
• bearings;
• actuators;
• moving dampers;
• stored mechanical energy;
• unexpected automatic operation.

An electrically isolated system may still contain mechanical hazards.

Before Testing the System

Before testing begins, the engineer should understand what the system is supposed to do.

Where available, review:

• the fire strategy;
• smoke control design information;
• cause-and-effect documentation;
• as-fitted drawings;
• fan and damper schedules;
• electrical schematics;
• previous service records;
• commissioning records;
• airflow and pressure results;
• manufacturers' maintenance instructions;
• details of normal and secondary power supplies;
• records of subsequent alterations.

A fan running does not prove that the smoke control system is working correctly.

The engineer needs to know which fan should run, which dampers should open or close, which areas should remain unaffected and what the intended ventilation strategy actually is.

Where reliable design information is missing, this should be recorded as a limitation.

Observed operation should not automatically be treated as correct operation.

Suggested Mechanical Smoke Ventilation Service Scope

1. General Visual Inspection

Inspect accessible equipment for:

• physical damage;
• water ingress;
• corrosion;
• contamination;
• loose equipment;
• damaged enclosures;
• damaged cables;
• obstructed vents;
• inaccessible equipment;
• unauthorised alterations;
• abnormal control panel indications;
• disconnected equipment;
• temporary repairs.

Roof-mounted equipment and plant-room equipment often deserve particular attention because of environmental exposure and general building-services activity.

2. Control Equipment

Inspect and functionally test the smoke control equipment.

Checks may include:

• normal indications;
• fault indications;
• fire condition operation;
• manual controls;
• firefighter overrides;
• local and remote switches;
• monitored circuits;
• communications between networked controllers;
• fan start commands;
• damper commands;
• feedback signals;
• fault monitoring;
• standby fan commands;
• interfaces with the fire alarm system.

The observed sequence should be checked against the documented cause and effect.

3. Smoke Dampers and Ventilators

Operate smoke control dampers and ventilators and confirm, where applicable:

• correct opening;
• correct closing;
• full travel;
• end-position feedback;
• absence of obstruction;
• actuator condition;
• linkage condition;
• correct operation for the selected fire zone;
• correct behaviour in unaffected areas.

The test should establish that the damper or ventilator does what the smoke control strategy requires, not simply that it moves.

4. Extract and Supply Fans

Fans should be inspected and operated sufficiently to establish their condition.

Checks may include:

• correct fan selection;
• correct direction of rotation;
• abnormal noise;
• abnormal vibration;
• bearing condition;
• mounting condition;
• flexible connections;
• belts where fitted;
• guards;
• motor condition;
• local isolators;
• contactors;
• motor protection;
• VSD or soft-start operation;
• duty and standby changeover.

Where possible, fans should be run under meaningful operating conditions.

A fan that is briefly jogged or allowed to run for only a few seconds may not reveal faults that appear under sustained load.

Electrical Supplies and Automatic Transfer Switches

The electrical supply is a fundamental part of a mechanically powered smoke control system.

Simply operating an ATS test switch and observing that the fan starts does not amount to a full electrical assessment of the supply arrangement.

Normal Supply

Checks may include:

• supply availability;
• correct voltage;
• phase-to-phase voltage;
• phase-to-neutral voltage where applicable;
• phase sequence;
• protective device condition;
• signs of overheating;
• supply monitoring;
• control voltage supplies.

Secondary Supply

Where a secondary supply is provided, the system should be tested to establish that it can operate from that supply as intended.

This may include:

• simulation of normal supply failure;
• automatic transfer;
• secondary supply availability;
• generator start where applicable;
• voltage on the secondary source;
• phase sequence;
• operation of the connected smoke control plant;
• restoration of the normal supply;
• automatic retransfer where designed;
• associated alarms and indications.

Testing an Automatic Transfer Switch

An ATS test should establish more than whether the mechanism physically changes position.

Depending on the installation, useful checks may include:

1. Record the condition of the normal supply.
2. Measure the relevant voltages.
3. Confirm phase sequence where applicable.
4. Establish the connected load.
5. Simulate loss of the normal supply using the intended test method.
6. Confirm automatic transfer to the secondary source.
7. Verify the secondary source electrically.
8. Confirm correct operation of the connected smoke control plant.
9. Confirm correct fan rotation.
10. Confirm correct operation of VSDs or starters.
11. Restore the normal supply.
12. Confirm correct retransfer.
13. Check for abnormal alarms or faults.
14. Inspect the switching equipment for abnormal heating or other signs of deterioration.

The exact procedure should follow the equipment manufacturer's instructions and the system design.

Energised Electrical Testing

Some useful electrical checks cannot realistically be completed with the equipment dead.

Examples include:

• measuring operating voltage;
• checking phase sequence;
• checking voltage on both ATS supplies;
• measuring running current;
• comparing phase currents;
• observing voltage during transfer;
• investigating voltage imbalance;
• diagnosing contactor or VSD faults;
• carrying out thermal inspection under load.

This does not mean routine live working should be accepted.

Wherever reasonably practicable, electrical work should be carried out dead.

Some electrical testing and fault finding will, however, require the equipment to be energised.

Where this is necessary, the work should be properly assessed and carried out by someone competent for the task using suitable test equipment and safe working practices.

The fact that the equipment forms part of a fire safety system does not remove the requirements of the Electricity at Work Regulations.

Thermographic Inspection

Thermal imaging can be a useful condition-monitoring tool when inspecting smoke control electrical equipment.

Equipment that may be worth checking includes:

• ATS terminals;
• contactors;
• MCCBs;
• isolators;
• busbars;
• cable terminations;
• VSD connections;
• motor connections;
• distribution equipment supplying smoke control plant.

Thermal inspection can help identify abnormal heating associated with:

• high-resistance connections;
• deteriorating contacts;
• abnormal loading;
• phase imbalance;
• loose terminations.

Thermography is most useful when the equipment is carrying a representative load.

A poor termination carrying very little current may show little or no abnormal heating.

Care is also needed when interpreting temperatures on polished or reflective electrical surfaces. Emissivity and reflected heat can affect the displayed temperature.

Thermal imaging should therefore be used as a condition-monitoring tool, not as a replacement for electrical testing.

Running Current and Phase Comparison

Where appropriate, fan motor current can provide useful information about system condition.

Three-phase readings may help identify:

• current imbalance;
• abnormal loading;
• motor problems;
• supply problems;
• mechanical loading issues.

Measurements should be considered alongside:

• motor nameplate information;
• VSD information;
• design duty;
• measured airflow;
• previous service results.

An abnormal reading is a reason to investigate further. It is not necessarily a diagnosis by itself.

Functional Cause-and-Effect Testing

Mechanical smoke control should be tested from its intended initiation points, not only from local overrides.

Depending on the design, testing may include activation from:

• automatic smoke detection;
• manual call points;
• dedicated smoke control detection;
• sprinkler interfaces;
• firefighter controls;
• local manual controls.

For each test condition, verify the complete sequence.

This may include:

1. The correct fire zone is recognised.
2. The correct smoke damper opens.
3. Dampers in unaffected areas remain in the required position.
4. The replacement-air route opens.
5. The extract fan starts.
6. The supply fan starts where applicable.
7. The correct duty fan operates.
8. Standby equipment remains available.
9. Other relevant interfaces respond correctly.
10. The correct indications appear at the smoke control panel.
11. Manual firefighter controls operate correctly.

The purpose is to prove the intended system sequence, not simply that individual components are capable of operating.

Duty and Standby Equipment

Where redundancy is provided, the standby arrangement should also be tested.

A system containing two fans has not demonstrated redundancy merely because both fans can be started individually.

Where automatic standby operation forms part of the design, testing should establish what happens when the duty equipment fails.

This may involve simulation of:

• fan failure;
• zero airflow;
• starter failure;
• relevant monitored fault conditions.

The standby equipment should then operate in accordance with the design.

Performance Testing

Functional operation and system performance are not the same thing.

A fan can:

• start;
• rotate in the correct direction;
• draw current;
• show no fault;

and still fail to provide the airflow required by the design.

Where performance testing forms part of the maintenance requirement, measurements may include:

• volumetric airflow;
• air velocity;
• pressure differential;
• shaft extract rate;
• pressure across doors;
• door opening forces where relevant;
• fan operating conditions.

Results should be compared with commissioning data or documented design criteria where available.

A measured value has limited meaning if there is nothing reliable to compare it with.

Maintenance Frequency

Smoke control systems should be subject to a planned testing and maintenance regime.

The exact regime should be established from:

• the applicable smoke control standard;
• the fire strategy;
• system design information;
• manufacturers' instructions;
• the fire risk assessment;
• previous inspection findings;
• the complexity of the installation.

Routine building-management checks and specialist engineering maintenance should not be treated as the same thing.

A routine test may show that the system responds.

A specialist maintenance visit should go further and establish whether the system remains in a condition where it can reasonably be expected to perform its intended function when required.

Recording Limitations

Maintenance records should clearly state what has and has not been tested.

For example, an engineer may have confirmed:

• fire alarm initiation;
• smoke control panel response;
• damper operation;
• fan operation.

But they may not have tested:

• the secondary electrical supply;
• the ATS;
• electrical condition;
• airflow performance;
• standby fan operation.

If so, that should be recorded.

A system should not be described as fully serviced or fully tested where significant parts of it were outside the scope of the visit or outside the competence of the attending engineer.

Where work requires competence that the attending engineer does not hold, the limitation should be recorded and the work referred to someone suitably competent.

Fire Alarm Engineer Does Not Mean Smoke Control Engineer

Fire alarm systems and smoke control systems often interact, but they are not the same engineering discipline.

Competence to maintain a fire alarm system does not automatically demonstrate competence in:

• three-phase electrical systems;
• motor control;
• automatic transfer switches;
• VSDs;
• airflow measurement;
• mechanical ventilation;
• pressure differential systems;
• fan performance;
• smoke control design.

The opposite also applies.

An electrically competent engineer is not automatically competent to assess smoke control cause and effect, airflow performance or system design.

Companies maintaining these systems should define competence by task and system, rather than relying on broad job titles such as "fire engineer" or "fire alarm engineer".

Some installations will require more than one discipline to be involved.

Example Competence Matrix

This table is illustrative only.

Actual competence should be assessed against the specific equipment, task and hazards involved.

Key Principle

Mechanical smoke ventilation should be treated as a complete life-safety engineering system.

A satisfactory service is not simply:

Activate fire alarm, fan runs, pass.

The engineer should establish, as far as required by the maintenance regime, that:

• the correct equipment operates;
• the controls follow the intended sequence;
• dampers and ventilators operate correctly;
• fans remain mechanically serviceable;
• electrical supplies are available and suitable;
• secondary power operates when required;
• automatic transfer equipment functions correctly;
• duty and standby arrangements work;
• system faults are correctly monitored;
• performance remains consistent with the design intent;
• testing has been carried out by people competent for the work undertaken.

Where parts of the system cannot be tested safely, are outside the agreed scope or fall outside the competence of the attending engineer, those limitations should be clearly recorded and referred for suitable specialist attention.

The point of servicing is not to produce a certificate.

It is to establish whether the smoke control system is actually likely to work when it is needed.