Nebosh_Sample_Q_a

ELEMENT 8: CONSTRUCTION ACTIVITIES – HAZARDS AND CONTROL Short Questions 1. Outline the main hazards that may be expected during the demolition of a multi-storey building. (8 marks) The main hazards found during the demolition of a multi-storey building are: Falls from height Falling debris and premature collapse of building The use of explosives Noise from equipment and heavy plant Production of dust, possibly including asbestos Hazardous materials from previous uses of the building Cellars, vaults and voids affecting the stability of adjacent premises The presence of services (not necessarily underground services), e.g. gas, electricity and water 2. Identify the main hazards associated with excavation work on a construction site. (8 marks) The main hazards associated with excavations are: Falls of persons/equipment/material into excavations. Contact with buried services. Vibration caused by machinery and vehicles nearby may lead to the collapse of the excavation. Loose or unstable earth around an excavation or at the bottom may collapse. Water ingress or flooding may occur. There may be contaminated ground at the site of excavation. Digging may uncover buried materials or contaminated toxic and asphyxiating atmospheres hazardous to health. Vehicles (e.g. mobile cranes, mobile plant) may fall into the excavations. Vehicles passing too close to an excavation may cause the sides to collapse. 3. (a) Give FOUR reasons why something may fall from a height, on a construction site. (4 marks) On a construction site, something may fall from a height due to: Deterioration of the structure Inappropriate storage Poor housekeeping Gaps in the platform Lack of edge protection Incorrect methods for lifting or lowering (b) Describe FOUR control measures to prevent items falling from a height. (4 marks) Control measures to prevent items falling from a height are: Physical safeguards – barriers, close boarding, use of nets and toe boards Supervision Good housekeeping Procedures and safe systems of work 4. (a) Outline the main hazards associated with the use of ladders at work. (3 marks) The main hazards associated with the use of ladders at work are: Poor maintenance Incorrect use of the ladder Incorrect footing (b) Describe how a ladder hazard may be eliminated or reduced. (5 marks) Ladder hazards may be eliminated or reduced by: Correct inspection. Correct storage. Correct securing. The correct angle (1:4 or 75° to the horizontal) Correct section use Training of operators Tied to structure Footed 5. Identify EIGHT safe practices to be followed when using a skip for the collection and removal of waste from a construction site. (8 marks) Safe practices when using a skip to collect and remove waste from a construction site are: Making sure the skip is of sound construction. Locate skip on firm, level ground away from excavations. Clear access for filling the skip and its removal by a vehicle away from the site Filling by means of a chute or mechanical means (unless done by hand) Controls to prevent over-filling Controls to prevent tipping (disposal) of incompatible wastes Use of netting or sheeting covers when skip is full Fire safety procedures Need to site away from buildings Need to protect against arson 6. Maintenance workers are replacing fluorescent tubes in the roof space of a busy warehouse using a mobile elevating working platform (MEWP). (i) Identify the possible hazards associated with the task. (8 marks) (ii) Outline measures to be taken to ensure the safety of the maintenance workers and others who may be affected by the work. (12 marks) (i) The hazards associated with the task would include: Working at height with the possibility of falling Coming into contact with electrical fittings Trapping in the mechanism of the MEWP Instability of the MWEP caused by sloping or uneven floors Being struck by an overhead travelling crane Collision between a vehicle and the MEWP Materials and tools falling from a height Contact with broken glass Environmental hazards such as excess heat, insufficient Lighting and dust exposure (ii) The control measures that should be taken to ensure the safety of the maintenance workers and the other employees: Choosing a time to carry out the work when the warehouse is less busy Correct positioning of the MEWP. Avoiding slopes and uneven floors Ensure outriggers are fully extended and locked in position and brakes applied before the platform is raised. Ensure that guardrails are fitted to the platform. Arrange for the isolation of the overhead cranes to prevent their movement. Make sure that the platform of the MEWP is lowered before moving to a new position. Use barriers and warning signs to prevent access of other people into the working area. Establish the competence of the MEWP driver and maintenance workers involved in replacing the fluorescent tubes. 7. Damaged corrugated roofing sheets on a single storey factory are to be replaced. Access to the roof will be via a mobile tower scaffold. (i) Identify the hazards likely to be encountered during such work. (6 marks) (ii) Outline the precautions needed to ensure the safe use of the mobile tower scaffold. (6 marks) (iii) Outline further precautions that may be required to control the hazards identified in part (i). (8 marks) (i) The hazards associated with working on the mobile tower scaffold would include: Working at height with the possibility of falling Falls of material Exposure to extreme weather conditions Use of work equipment, including access equipment Manual handling Work on or near fragile roofing materials Overhead electrical line Contact with hazardous substances, including asbestos (ii) The precautions needed to ensure safe use of the mobile tower scaffold include: Ensuring that the ratio of the height of the tower to its base dimension is correct The provision of adequate diagonal bracing A working platform which is fully boarded with toe boards and guardrails in place A safe means of access to the platform Means of locking the wheels of the tower when work is being carried out The use of outriggers Checking that the condition of the ground on which the tower is sited is suitable (i.e. level and firm) Only competent people erect and inspect the scaffold. (iii) Further precautions required to control hazards encountered when replacing roofing sheets: Provision and use of roof ladders Crawling boards Protection of roof edges and voids Harnesses The provision of hoists chutes and covered skips for the removal of old roof materials. Protection of those working below (e.g. barriers, netting, signs, safety harnesses) Isolation of overhead services (electricity) and ensuring safe distances Use of low reduced voltage or RCDs for portable electric tools Protection against extreme weather conditions Suitable precautions if asbestos sheeting involved, (i.e. avoid breaking up asbestos sheeting, use of respiratory protection, overalls, damping down, ensuring safe disposal of waste). 8. Outline the precautions that should be taken to reduce the risk of injury when work is carried out on pitched roof Carry out roof survey prior to work starting Safe means of access to roof Roof edge barriers Roof ladders or crawling boards provided Identifying and covering roof lights Facilities to raise and lower materials safely Protection for persons below Provision for persons below Provision of safety harnesses if necessary Avoid working in severe adverse weather conditions Competent workers and supervisors 9. Outline the main precaution to be taken when carrying out excavation work The precautions that need to be taken for excavations include: Not to undermine nearby structures Underground services The type of soil To prevent collapses Prevent persons falling into the excavation Prevent vehicles falling into the excavation Ensure safe access and egress Precautions against gases Checking if the soil in contaminated Provision of lighting Competent and trained staff Emergency procedures Personal protective equipment 10. Outline 8 precautions that may be taken to ensure the safety of children who might be tempted to gain unauthorised access to a construction site The precautions for preventing children trying to gain access may include: Fencing Hoardings Warning signs Security patrols Visiting schools Viewing panels Should access be gained then the following precautions should be taken: Covering or fencing excavations Removing ladders Immobilising plant and machinery Locking away chemicals and tools Isolating services Clearing away rubbish and debris 11. Outline five factors that may contribute to the collapse of an independent tied scaffold Wrong materials Unstable foundations Improperly designed Improper erection Overloading Modified incorrectly Undermined by excavations Hit by machinery Excessive winds/rain 12. Outline 8 health and safety precautions that should be taken when undertaking demolition work The main safety precautions should be: Identification and isolation of services Barriers and fences Restricted access Means of preventing falls from height Use of elephant trunks for debris removal Competent staff Means of suppressing dust Identification and correct removal of hazardous substances Preventing premature collapse (building and adjoining buildings) Properly maintained equipment Sequence of demolition followed Responsibilities understood. 13. Outline the precautions when using step ladders in the workplace Ensure that the step ladder is inspected for defects before use Correctly erected on level ground with its chain or rope fully extended Suitable for the task to be performed and does not involve carrying out work from the top step Footed by a second person when necessary Correctly positioned to avoid over reaching Not overloaded Positioned on even ground Close to work to avoid overreaching 14. Identify the factors to be considered when using a mobile elevated work platform When using a MEWP make sure: The operator is fully trained and competent The work platform is fitted with guard rails and toe boards It is used on suitable firm and level ground. The ground may have to be prepared in advance Not overloaded Clear of overhead obstructions The work area is cordoned off to prevent access below the work platform and collisions Any outriggers are extended and chocked as necessary before raising the platform Everyone knows what to do if the machine fails with the platform in the raised position. If being used on a public highway in poor lighting that it is well lit.