Write a risk assessment for FAHU replacement

A suitable safe system of work for replacing a Fresh Air Handling Unit (FAHU) should begin with a task-specific risk assessment, coordination with the client/site operator, and a permit-to-work package covering isolation, lifting, work at height, electrical work, hot work if applicable, and any confined-space elements. The work area should be defined, access restricted, and the sequence planned so the unit is shut down, isolated, proved dead, mechanically secured, disconnected, removed, and replaced in a controlled order by competent persons. [1] [3] [5]

Key hazards to assess

• Electrical shock, arc/flash, unexpected energization, and induced or back-fed power
• Mechanical hazards from fans, belts, dampers, actuators, rotating parts, stored spring force, and moving sections
• Release of stored energy from pressurized pipework, steam/hot water/chilled water, pneumatics, hydraulics, and gravity
• Dropped objects, suspended loads, crane or hoist failure, and struck-by/crush hazards during lifting
• Falls from roofs, platforms, ladders, scaffolds, or aerial lifts, plus fragile surfaces and openings
• Manual handling injuries from ductwork, panels, motors, filters, coils, and awkward access
• Exposure to asbestos-containing materials in older insulation, boards, gaskets, coatings, or surrounding building fabric
• Refrigerant exposure, oxygen displacement, cold burns, toxic decomposition products, and environmental release if coils or connected systems contain refrigerant
• Hot work hazards if cutting, grinding, brazing, or welding is required
• Slip, trip, housekeeping, noise, sharp edges, weather, and restricted-access hazards

[7] [12] [13] For HVAC isolation and lockout/tagout, identify all energy sources before work starts: electrical supplies, local isolators, BMS/controls, interlocks, VFD feeds, standby supplies, actuators, dampers, fan rotation, and any connected water, steam, condensate, gas, compressed air, or refrigerant services. Shut down the FAHU, isolate each source with an energy-isolating device, apply personal locks and tags, release stored energy, block moving parts, and verify zero energy by test/try-out before touching conductors or mechanical components. Control-circuit buttons and selectors are not acceptable isolation points on their own. [9] [9] [14]

Where ducts, coils, or connected services could introduce hazardous energy or material, use positive isolation appropriate to the risk. For pipework or ducts carrying hazardous substances or pressure, do not rely on a single valve where complete isolation is required; use methods such as blanking/blinding, removing sections, or double block and bleed where necessary. Drain, vent, purge, and prove isolation before breaking connections. Secure dampers, fan impellers, and access doors against movement. [9] [9] [8]

Recommended work sequence

1. Survey the FAHU location and access route; confirm structural capacity, dimensions, lifting path, weather exposure, and whether roof work, confined space entry, or hot work permits are needed.
2. Review asbestos information, O&M manuals, drawings, electrical schematics, and refrigerant/system details before intrusive work.
3. Issue permits to work and brief all workers and contractors on hazards, controls, emergency arrangements, and stop-work criteria.
4. Shut down the system in a controlled manner and notify affected occupants/users.
5. Isolate and lock out all electrical and mechanical energy sources; drain, vent, and isolate connected services; verify zero energy.
6. Establish exclusion zones below and around the work and lifting area with barricades and signage.
7. Remove panels, filters, belts, motors, coils, duct connections, and fixings in a planned sequence to reduce weight and instability.
8. Use suitable lifting equipment and a lifting plan to remove the old FAHU or modules; never allow anyone under suspended loads.
9. Install the replacement unit, reconnect services, inspect supports/anchors, and verify guards, access panels, and drainage.
10. Before re-energization, remove tools and temporary restraints, confirm all persons are clear, remove locks under procedure, test run, check rotation/airflow/vibration, and hand back the system.

[1] [13] [15] Electrical safety controls should include competent electrical persons, identification of all supplies, proving dead with an approved test instrument, insulated tools where appropriate, protection from exposed live parts nearby, and control of temporary power. If testing or commissioning requires energization, this should be separately planned, authorized, and minimized. Faulty electrical equipment must be removed from service, and equipment used in hazardous atmospheres or restricted spaces should be suitable, grounded, and, where needed, explosion-proof or low-voltage. [5] [14] [15]

Mechanical hazards during FAHU replacement include rotating fans, belts, pulleys, dampers, actuators, spring-loaded components, sharp sheet-metal edges, hot surfaces, and stored pressure. Controls should include full shutdown, LOTO, blocking against motion, securing moving parts, allowing hot components to cool, draining coils and pipework, and using cut-resistant gloves where appropriate. Good housekeeping is essential to prevent slips, trips, and falls during dismantling and installation. [12] [8] [11]

Lifting operations for the FAHU should be planned by a competent person and executed by trained operators/riggers using equipment with adequate capacity and inspection status. Confirm the weight and center of gravity of the unit or modules, lifting points, sling angles, route, landing area, and structural capacity of roofs or floors. Establish a no-go zone, use tag lines where appropriate, protect against falling objects, and never work under suspended loads. Inspect cranes, hoists, hooks, chains, wire rope, and synthetic slings before use, and do not exceed rated capacities. [13] [13] [17]

For work at height, use the safest practicable access method: fixed platforms, scaffold towers, MEWPs/aerial lifts, or ladders only for short-duration low-risk tasks where justified. A site-specific fall protection plan should identify all fall hazards, protection methods, overhead hazard controls, tool/material securing methods, and rescue arrangements. Workers in aerial lifts should use the required harness/lanyard arrangement, keep gates closed, stand on the platform floor, avoid overreaching, and not use ladders or planks in the basket. Stop work in high winds or adverse weather, and protect people below from dropped objects with barricades, toe boards, nets, or overhead protection. [16] [15] [13]

Manual handling risks are significant during FAHU replacement because components are often bulky, sharp-edged, and awkward in posture-constrained plant rooms or roofs. Reduce risk by breaking the unit into smaller modules where possible, using mechanical aids, team lifts, dollies/skates, and planned routes free of trip hazards. Avoid twisting while carrying, keep loads close to the body, and set realistic weight limits based on access and posture rather than weight alone. [7] [11]

Asbestos must be considered before disturbing any older insulation, gaskets, boards, fireproofing, duct insulation, floor tiles, or surrounding building materials. If asbestos-containing material is suspected, stop work until the material is identified. Sampling and assessment should be arranged by competent persons, and any removal or disturbance should follow the applicable asbestos control plan and legal requirements. Controls include restricting access, warning signage, wet methods, HEPA-filtered respiratory protection where required, suitable disposable protective clothing, approved tools/extraction, and compliant waste packaging and disposal. Dry sweeping and compressed air should not be used. [6] [6] [6]

Refrigerant considerations depend on whether the FAHU includes or is connected to refrigerant-containing coils or DX equipment. Before disconnection, identify the refrigerant type and quantity, isolate the system, and arrange recovery by trained and authorized personnel using suitable recovery equipment. Main hazards include pressure release, cold burns/frostbite, oxygen displacement in enclosed areas, and toxic decomposition products if refrigerant contacts flames or hot work. Ventilation should be maintained, ignition sources controlled, and cylinders secured and handled upright. If refrigerant release is suspected in an enclosed plant area, evacuate, ventilate, and prevent re-entry until the atmosphere is confirmed safe.

Permit-to-work controls should normally include, as applicable: LOTO/energy isolation permit, electrical permit, hot work permit, lifting plan/permit, roof or work-at-height permit, and confined-space permit if entry criteria are met. Permits should define the task, location, authorized persons, hazards, isolations, PPE, equipment, validity period, emergency contacts, and hand-back arrangements. Where contractors are involved, host employer and contractor coordination is essential. [1] [3] [5]

If any part of the FAHU replacement involves entry into a space meeting confined-space criteria, comply with permit-required confined-space controls: complete the permit, isolate all energy and connected lines, test the atmosphere before entry and as needed during occupancy, provide ventilation, maintain communication, station an attendant/safety standby outside, and ensure rescue arrangements are in place. Typical acceptable entry conditions include oxygen between 19.5% and 23.5% and flammable gas below 10% LEL. [14] [10] [2]

PPE typically required

• Hard hat
• Safety glasses or goggles; face shield for cutting/grinding or splash risk
• Cut-resistant and task-appropriate gloves; chemical-resistant gloves where needed
• Safety footwear with toe protection and slip-resistant soles
• Hearing protection where noise levels require it
• Hi-vis clothing where vehicle or lifting plant movement exists
• Fall-arrest harness/lanyard for MEWP or other specified fall-protection systems
• Respiratory protection selected to the hazard, such as dust/asbestos or refrigerant-related exposure, with fit testing and training where required
• Protective clothing/disposable coveralls where contamination, asbestos, or sharp/dirty work is present

[1] [5] [4] Emergency procedures should be briefed before work starts and matched to the hazards present. They should cover electrical shock, falls from height, dropped loads, fire, refrigerant release, asbestos disturbance, medical emergencies, and any confined-space rescue needs. Emergency contacts, first-aid arrangements, rescue equipment, communication methods, and access for emergency services should be confirmed. For confined spaces, rescue must not rely on improvised entry by unprotected coworkers; standby/rescue arrangements, retrieval equipment where needed, and trained responders should be in place before entry. [3] [8] [16]

From a compliance standpoint, the FAHU replacement should satisfy the core principles of both HSE-style and OSHA requirements: suitable and sufficient risk assessment; competent supervision and trained workers; safe isolation/LOTO; permit-to-work where required; safe access and fall protection; planned lifting operations; PPE based on hazard assessment; control of hazardous substances including asbestos and refrigerants; emergency preparedness; inspection of equipment; and coordination between host employer and contractors. In OSHA terms, this aligns particularly with hazardous energy control, permit-required confined spaces where applicable, fall protection, aerial lift safety, PPE hazard assessment, and safe lifting/struck-by prevention. In HSE terms, it aligns with risk assessment, safe systems of work, work at height, lifting operations, asbestos management, COSHH-style substance control, and contractor management. [4] [9] [16]