Admittedly there is no one size fits all approach to the retention of health and safety records, so I can understand why to keep everything seems like the safest option but there is guidance out there to help you make the decision on record retention.
L8, Legionnaires’ disease, the control of Legionella bacteria in water systems states a 5-year retention for any Legionella monitoring records and 2 years for your management information (risk assessment, written scheme, etc.). Whereas the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations (RIDDOR) states that all accident records and associated documentation must be kept for 3 years - as a civil claim can be brought against an organisation up to three years after the date of the accident/injury. However, your declaration of conformity for lifts under the Lifting Operations and Lifting Equipment Regulations (LOLER) need to be kept for the lifetime of the equipment.
Where regulations do not specify how long records should be kept for, the common practice amongst the industry and recommendation from various legal firms identifies a 5-year retention strategy as best practice.
Of course, there are exceptions to this with health surveillance records relating to the Control of Substances Hazardous to Health and asbestos records, for example, needing to be kept for a minimum of 40 years. The Health and Safety Executive also state “where regulations do not specify how long they should be kept for, the health record should be kept at least while you employ the worker” and “it is good practice to offer workers a copy of their health record when they leave your employment or if you cease trading.”
Although not completely clear cut, this should give you the confidence to throw out some of those archived monitoring folders you may no longer need or require.