Turbulent vs laminar airflow – at the time of the growing number of devices inside the sterile area

Background of case study:

  • The laminar (low turbulent) airflow used to be considered optimal for the surgical field protection
  • Due to the growing number of devices inside the sterile area, the laminar airflow principles are not fulfilled anymore
  • Constant pressure and laminar flow type of air stream (generated by a diffuser) is breached hitting the devices inside – or at the border of clean and dirty areas breaking the laminar principle (or stopping the flow completely), creating an uncontrolled flow of air in terms of direction and velocity

Computer Fluid Dynamics


Computer Fluid Dynamics (CFD) simulation of the laminar stream being breached by the C-arm located in a sterile field

Software ANSYS CFD


Computer Fluid Dynamics CFD

Key finding:

Plane 2 flow breaking generates chaotic air mixing underneath the C-arm intensifier causing uncontrolled direction and velocity of the stream → Less control on protective air cushion inside the sterile area.

Karolinska University Hospital – a future-proof setup


  • Ventilation setup based on individual requirements of different surgical disciplines – conditions and energy consumption optimization
  • Flexibility; more ceiling and floor space for equipment and instrument carts/tables
  • Economical factor; low operation cost
  • Surgical environment; thermal comfort improved
  • Microbiological safety: < 5 CFU*/m³

* CFU – Colony-forming unit

Karolinska University operation

Operating theater of Karolinska Solna validated on June 2016

Time of operative phase: 45 minutes

Personnel of 10 inside the room


Max. concentration: 4 CFU

Average concentration: 1,5 CFU



Sterile surgical room, < 5 CFU/m3

Karolinska University3

Turbulent vs laminar airflow – at the time of the growing number of devices inside the sterile area

Turbulent airflowcore assumptions:

  • To restore control over the direction of airflow using the advanced setup of diffuser’s stream.
    Higher, precisely directed velocity = controlled turbulence*.

Additional assumptions:

  • To guarantee the microbiological safety of <5 CFU/m3 through the whole space of surgical room – in optimal conditions the laminar air diffusers system is able to achieve so only in the sterile zone
  • Reduction of negative temperature differences (clean vs dirty area) thermal effect
  • To release the ceiling space for additional equipment (monitors, pendants, lights, columns) thanks to circuit diffusers setup
  • Energy consumption optimization
  • Programmable solution

* If nowadays the turbulence is being created (due to number of obstacles) no matter which solution is used, the key is to take control over it and direct the stream out of the sterile zone

Independent Validation (MyAir Test and Validation)



Average: 1,5 CFU/m3

Maximum local: 4,0 CFU/m3



Turbulent AF circuit installation

Laminar AF area

Measurements points: surgical field, instruments tables


Turbulent vs laminar airflow

turbulent vs laminar

Laminar airflows:

  • Higher level of CFU inside the sterile area caused by flow disturbance underneath the C-arm intensifier
  • Higher level of CFU outside the sterile area. Most critically the issue of microbiological safety around the tools and elements being processed through dirty and clean areas

5000 m3/h Halton Vita Space  Halton Vita Space

5000 m3/h laminar airflow →      laminar air flow

Safety is the key!

  • Microbiological safety = fewer infections, healthier results
  • Personel’s thermal comfort = improved standard and quality of performance
  • Effective usage of ceiling and floor spaces

Source: www.halton.com