Public Health Agency

Hierarchy of controls

Hierarchy of controls

This section is included to support organisations/employers that have a responsibility to assess, manage and monitor risk in the context of managing infectious agents based on the measures as prioritised in the hierarchy of controls.

Risk assessments must be carried out in all areas by a competent person with the skills, knowledge and experience to be able to recognise the hazards associated with respiratory infectious agents. This can be the employer, or a person specifically appointed to complete the risk assessment. During development and on completion this risk assessment needs to be communicated to employees. This can be used to populate local risk management systems. Risk assessments must be revisited when any element of the original risk assessment changes in any way for example clinical specialty, patient vulnerability, staff, building and environment.

The hierarchy of controls can be used to help implement effective controls and reduce the spread of respiratory pathogens in health and care settings, these are applied in order and are used to identify the appropriate controls. Safe systems of work outlined in the hierarchy of controls, including elimination, substitution, engineering, administrative controls and PPE/RPE, are an integral part of IPC measures. The risk assessment should include evaluation of the ventilation in the area, operational capacity, and prevalence of infection/new variants of concern in the local area.


The idea behind this hierarchy is that the control methods at the top of graphic are potentially more effective and protective than those at the bottom. Following this hierarchy normally leads to the implementation of inherently safer systems, where the risk of illness or injury has been substantially reduced.

Some of the key areas and measures that could be considered are outlined below.


Elimination (physically remove the hazard)

The most effective measures in the hierarchy of controls are those that eliminate the risk. This requires organisations/employers to redesign the activity so that the risk is removed or eliminated, key mitigations may include:

  • screening, triaging and/or testing for SARS-CoV-2 and other respiratory pathogens relevant to the setting, for example RSV or influenza. This must be undertaken to enable early recognition and to clinically assess patients prior to any patient attending a healthcare environment.
  • where treatment is not urgent consider delaying this until resolution of symptoms providing this does not impact negatively on patient outcomes
  • staff should not attend work if symptomatic/infectious

Substitution (replace the hazard)

When a source of infection cannot be eliminated substitutions should be implemented to reduce or control the risk. This is sometimes not possible for health or care to achieve.

However, some services may be able to consider the use of virtual consultations (telephone or video).

Engineering controls (control, mitigate or isolate people from the hazard)

Engineering controls are used to reduce or control the risk of exposure at source.

They include design measures such as ventilation/barriers/screens. Priority should be given to measures that provide collective/maximal protection rather than those that just protect individuals or a small group of people, for example:

  • ensuring ventilation systems, mechanical or natural, meet national recommendations for minimum air changes. This should be carried out in conjunction with organisational estates teams/specialist advice from ventilation group and /or authorised engineer
  • dilute air with natural ventilation by opening windows and doors where possible
  • if considering screens/partitions in reception/waiting areas, ensure air flow is not affected and cleaning schedules are in place, consult with Estates/facilities teams
  • assess whether room provision is sufficient if there were to be an increase in patients requiring isolation for respiratory infection. Work in a multidisciplinary team with hospital leadership, engineering, and clinical staff to plan for creation of adequate isolation rooms/units
  • assess the function of care areas. Patients with respiratory infections should not be cared for in poorly ventilated/overcrowded areas. Where a clinical space has very low air changes and it is not practical to increase dilution effectively then consider alternative technologies with Estates/ventilation group


Administrative controls (change the way people work)

  • Administrative controls (for example the design and use of appropriate processes, systems and engineering controls, and provision and use of suitable work equipment and materials) are implemented to help prevent the introduction of infection and to control and limit the transmission of infection in health and care facilities. They include:
  • screening, triaging, and testing to enable early recognition of SARS-CoV-2 and other infectious agents, for example influenza, RSV
  • maintaining separation in space and/or time between patients with and without suspected respiratory infection by:
  • appointment or clinic scheduling to reduce waiting times in reception areas and avoid mixing of infectious and non-infectious patients
  • appropriate patient placement for infectious patients in isolation or cohorts
  • regular assessments of physical distancing and bed spacing, taking into account potential increases in staff to patient ratios and equipment needs (dependent on clinical care requirements)
  • for patients who are suspected or confirmed to be positive with a respiratory pathogen including SARS-CoV-2 and their treatment cannot be deferred, care should be provided from services able to operate in a way which minimises the risk of spread of the virus to other patients/individuals
  • provision of appropriate education for staff, patients and visitors in IPC
  • provision of additional hand hygiene stations (alcohol-based hand rub) and signage – to ensure good hygiene practices in staff, patients, and visitors
  • providing safe spaces for staff breaks areas/changing facilities
  • ensuring regular cleaning regimes are followed, and compliance monitored including that of reusable patient care equipment
  • ensuring staff and patients’ adherence with IPC guidance including face masks/coverings and physical distancing measures


Personal protective equipment

PPE is considered to be the least effective measure of the hierarchy of controls. PPE should be considered in addition to all previous mitigation measures in the hierarchy of controls, however it is acknowledged that not all elements of the hierarchy of controls will be possible in some settings for example in a patient’s home. PPE considerations include:

  • adequate supply and availability of PPE including RPE to protect staff, patients, and visitors
  • all staff required to wear an FFP3 mask have been fit tested (this is a legal requirement)
  • all staff (clinical and non-clinical) are trained in putting on removing and disposing of PPE
  • visual reminders are displayed communicating the importance of wearing face masks (if applicable), compliance with hand hygiene and maintaining physical distancing
  • PPE must be worn when exposure to blood and/or other body fluids, non-intact skin or mucous membranes is anticipated in line with standard IPC precautions and transmission based precautions

Where an unacceptable risk of transmission remains following the application of the hierarchy of controls risk assessment, it may be necessary to consider the extended use of RPE for patient care in specific situations.