Team Member Role(s) Profile
Paul Banaszkiewicz Paul Banaszkiewicz Section Editor
Lorgan Lorcan McGonagle Segment Author
  • Theatre design is an important component of any surgical curricula. Components of this module are readily asked as part of the written MCQ papers or as part of the basic science viva.
  • Knowledge of the principles of sterilisation, infection control and air flow are necessary to help prevent prosthesis-related infections and their potentially devastating consequences.
  • Issues surrounding patient consent are pertinent in daily clinical practice. Problems around consent and communication are a common source of litigation.
  • This section aims to describe the key components of theatre design and consent, which is useful for the FRCS exam as well as future clinical practice and leadership roles.

This is divided into three zones:


  • Provides outside to inside access
  • No traffic restrictions
  • Dress – street clothes are permitted
  • Patient receiving/holding areas
  • Dressing rooms
  • Lounges and offices


  • Authorised personnel only (patients and staff)
  • Provides access from an unrestricted area to a restricted area of the operating room (OR)
  • Dress: proper OR attire (scrubs, head and shoe covers) is required
  • Hallways
  • Instrument and supply processing area


  • Where surgical procedures are carried out
  • Authorised personnel only
  • Dress – proper OR attire including a mask must be worn in these areas1
  • Barn-type theatres with separate ultraclean air units exist with the proposed advantages of cost saving and easier supervision/teaching.
  • Peer awareness of contemporary surgical practice and standards.
  • There is no mixing of air between units/cabins.


Figure 1. Barn theatre


Figure 2. Barn type theatre design

  • An area of 55 m2 is recommended for all inpatient operating theatres.
  • A minimum clear height of 3000 mm between the finished floor level and ceiling is required to allow unrestricted adjustment of the operating luminaire and other ceiling-mounted equipment.
  • In an ultraclean air theatre, a preparation room can be excluded as instruments can be opened beneath the ventilation canopy.
  • Two theatres should not share the same preparation room to minimise the risk of cross-infection via ventilation air flows.


Figure 3. Typical operating site

  • Hygienic finishes:
  • Slip-resistant
  • Continuous
  • Smooth
  • Impervious
  • Sealed joints
  • Easily cleanable
  • Wear-resistant
  • For best practice, sterile services should be located on the same site.
  • The minimum space required in each anaesthetic room is 19 m2.
  • A small room is required for surgeons to record each completed operative procedure. The room should be located close to the operating theatres and can be shared by several people at one time. A desk with a computer terminal and external telephone is required.

Operating theatre departments that admit patients for emergency surgery should have the following services:

  • Emergency care (A&E department)
  • 24-Hour access to imaging, including scanning
  • Critical care
  • Laboratory services (pathology)
  • Inpatient acute services
  • The main inpatient operating theatre department in each NHS trust should be located centrally within an acute hospital development. Ideally, all the operating theatres in the hospital should be in one location with one recovery unit.


Figure 4. Location

  • The temperature most favoured by surgeons is 18.5–21°C; some prefer a range of 21–22°C. The critical ambient temperature desirable is 21°C. For infants and children this may be increased up to 24°C.
  • Several factors can influence patient temperature intra-operatively, namely type of surgery, age, duration of surgery, type of warming, type of anaesthetic (less with neuroleptic anaesthesia in a laminar flow theatre compared with general anaesthesia with a volatile anaesthetic or peridural anaesthesia with additional general anaesthesia.
  • The major correlates of greater intraoperative decrease in temperature were: (1) GA (v epidural) (P=0.003); (2) cold ambient OR temperature (P=0.07); and (3) advancing patient age.


Figure 5. Theatre temerature

  • Humidity is the amount of water present in the vapour phase and is measured in hygrometers.9
  • Absolute humidity is the mass of water present in a volume of gas and is expressed in mg/l:

HA = mass H2O (g)/volume of air (l).

  • Relative humidity is the ratio of water partial pressure to saturated vapour pressure at a given temperature, and usually quoted as a percentage:

HR (%) = 100 x PH2O/SVP H2O

  • The recommended humidity range in an operating room is 20–60% based on addendum d to ANSI/ASHRAE/ASHE standard 170-2008. Each facility should determine acceptable ranges for humidity in accordance with regulatory and accrediting agencies and local regulations.10
  • Elevated levels of humidity are uncomfortable and can be associated with increased risk of infection.11,12


Figure 6. Theatre humidity

  • The quality of operating theatre lighting is defined by a combination of the light’s illumination, shadow control and colour rendition and temperature.
  • Glare from over lighting a surface may be just as impeding as under lit conditions.
  • A balance between luminence and glare is vital in order clearly to identify different shapes, sizes and texture of three-dimensional structures.13
  • The design standard EN 12464 provides guidance on the different types of lighting levels available within the medical environment.14
  • All surgical facilities, where possible, should have natural daylight directly from windows, or by means of borrowed light from windows across corridors. Windows should be fixed closed.
  • Ceiling-mounted lighting should not be installed directly overhead in patient areas in the operating department. An awake or lightly sedated patient cannot avoid the glare when lying on a trolley or bed. If ceiling-mounted fittings are used they should be two-directional so that they can be adjusted to prevent unwanted glare. The lighting should be dimmable without flicker.15

Hospital environment

Illuminance (lux)

Colour rendition (RA)

General office



Examination room



Operating theatre



Operating cavity







Unit for the amount of light at a given point


Colour rendition index

The effect the light source has on the appearance of coloured objects


Fail safe

Back-up possibility in case of interruption of power supply. Light should be restored within 5 seconds with at least 50% of previous illuminance. Should be completely restored within 40 seconds.




Figure 7. Theatre lights

  • PACU should be directly contiguous to the OR area from which the greatest number of patients come.
  • There should be a direct entrance to the PACU from an OR corridor and a separate exit, preferably to a main hospital corridor.16


Figure 8. Theatre recovery

  • Conventional operating theatres have plenum ventilation with filtered air, using filters with an efficiency of 80–95% to remove airborne particles ≥5 µm.17
  • Plenum ventilation is a system of mechanical ventilation in which fresh air is forced into the spaces to be ventilated from a chamber (plenum chamber) at a pressure slightly higher than atmospheric pressure, so as to expel foul air.18
  • The ventilation system in theatre can be a recirculating or a non-recirculating system. Recirculating systems recirculate some or all of the inside air back to the operating room suites or some other part of the hospital. Non-recirculating systems, all air brought to the room is conditioned, outside air. When a recirculating system is used, the air return duct should have a HEPA filter built into the system.
  • Directional flow is usually from inside the operating theatre to outside (positive pressure).
  • Ventilation systems should operate at all times, although air exchange can be decreased during unoccupied hours.19


Figure 9. Clean air delivery

  • Air cleanliness is expressed as bacteria-carrying particles per cubic metre (BCP/m3) (or colony forming units (cfu) per cubic metre). It is measured with a microbiological air sampler (Casella slit sampler).
  • Twenty air changes per hour are necessary in order to obtain 50–150 cfu/m3 of air. In the UK, the limit is 35 cfu/m3 for an empty operating theatre and in activity it should not exceed 180 cfu/m3 for an average 5-minute period. In an ultra-clean air operating theatre the limit is 10 cfu/m3 sampled within 30 cm of the wound using conventional clothing. The limit is <1 cfu/m3 of air when total body exhaust gowns are used.17
  • Laminar flow is a type of flow in which the air travels smoothly or in regular paths, in contrast to turbulent flow, in which the fluid undergoes irregular fluctuations and mixing.
  • In laminar flow, the velocity, pressure and other flow properties at each point remain constant.20
  • May be vertical or horizontal.
  • Laminar airflow is usually restricted to an area in the centre of the operating theatre (room within a room principle).
  • Flow of air = 0.3 m per second and is not perceptible by the theatre staff.
  • Laminar flow is broken around obstacles, such as operating lights, but quickly reforms.
  • It has been shown significantly to decrease the rate of infection (´2.6) in arthroplasty.21,22BS10THEATREDESIGN10(aa).png


Figure 10(a) and 10(b) Laminar flow

  • HEPA (high efficiency particulate air) filters remove airborne particles of 0.3 µm and above with 99.97% efficiency.17


Figure 11. HEPA filters 

  • A dedicated scrub and gowning room for each operating theatre with sufficient space for a minimum of three people (minimum size 11 m2); one scrub and gowning room can be shared between two operating theatres, both of which should be directly accessible with sufficient space for a minimum of six people, with three people scrubbing back to back, and space between to prevent contamination (minimum size 16 m2).
  • Where a scrub room is shared between theatres, potential exists for the compromising of pressure gradients within and between the two theatres, with possible adverse consequences for infection control. Specialist engineering advice should always be sought.
  • A recessed scrub and gowning area in each theatre with sufficient space for a minimum of three people (minimum size 7 m2). In an operating theatre with a recessed scrub area it is essential that it is located away from the area containing laid-up instrument trolleys in order to prevent water contamination. Non-touch taps, scrub solution and nailbrush dispensers are required.


-Measurement of colony-forming units per cubic metre (CFU/M3 ) in theatre resulted in 27 CFU of bacteria / M3 with no Clostridium perfringens and no Staphylococcus aureus CFU. Where would this be considered acceptable?


1. Horizontal laminar flow theatre with the samples taken from the centre of the enclosure
2. Horizontal laminar flow theatre with the samples taken from the periphery of the enclosure
3. Plenum ventilated theatre
4. Vertical laminar flow theatre with the samples taken from the centre of the enclosure
5. Vertical laminar flow theatre with the samples taken from the periphery of the enclosure


  • 1. Kochs E, Blanc I, Pfeifer G. [Course of central body temperature in the laminar airflow operating room in various anesthesia procedures]. Anasth Intensivther Notfallmed 1986; 21(4): 203–206
  • 2. Legg AJ, Cannon T, Hamer AJ. Do forced air patient-warming devices disrupt unidirectional downward airflow? J Bone Joint Surg Br 2012; 94(2): 254–256.
  • 3. Scott CC, Sanderson JT, Guthrie TD. Choice of ventilation system for operating-theatres. Comparison of turbulent versus laminar-linear flow systems in operating-rooms and industrial clean rooms. Lancet 1971; 1(7712): 1288–1291.
  • 4. Everett WD, Kipp H. Epidemiologic observations of operating room infections resulting from variations in ventilation and temperature. Am J Infect Control 1991; 19(6): 277–282.
  • 5. Brock L. The importance of environmental conditions, especially temperature, in the operating room and intensive care ward. Br J Surg 1975; 62(4): 253–258.
  • 6. Frank SM, Beattie C, Christopherson R, et al. Epidural versus general anesthesia, ambient operating room temperature, and patient age as predictors of inadvertent hypothermia. Anesthesiology 1992; 77(2): 252–257.
  • 7. Alijanipour P, Karam J, Llinás A, et al. Operative environment. Orthop Res 2014; 32 (Suppl 1): S60–S80.
  • 8. Dyer I. Measurement of humidity. Anaesth Intens Care Med 2012; 13(3): 121–123.
  • 9. Dumbleton T, Clift L, Bayer SH, Elton E, Howarth PA, Maguire M. 2010 NHS Purchasing and Supply Agency (© Crown Copyright).