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Unit 6.2. Mechanical and mixed mode ventilation TB Infection Control Training for Managers at National and Subnation

Unit 6.2. Mechanical and mixed mode ventilation TB Infection Control Training for Managers at National and Subnational Level. Objectives. After this unit, participants will be able to: Understand the principles of mechanical and mixed mode ventilation

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Unit 6.2. Mechanical and mixed mode ventilation TB Infection Control Training for Managers at National and Subnation

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  1. Unit 6.2. Mechanical and mixed mode ventilationTB Infection Control Training for Managers at National and Subnational Level

  2. Objectives After this unit, participants will be able to: • Understand the principles of mechanical and mixed mode ventilation • Describe the importance of maintenance for all ventilation systems Note: A public health manager should understand the principles and applicability and when to consult a ventilation engineer

  3. Outline A. Principles of mechanical ventilation • Single pass vs. recirculated • Air mixing • Negative pressure • Exhaust ventilation B. Mixed mode ventilation • Fans C. Maintenance and monitoring for all ventilation systems

  4. A. Mechanical ventilation • Is created by using a fan to force air exchange and to drive air flow • Works by generating negative pressure in the room to drive airflow inward To be effective, it is essential that: • All doors and windows kept closed • A minimum of 12 ACH is maintained • The ventilation system is well-designed, maintained and operated

  5. Principles of ventilation • Which is an easier way to extinguish the flame? • Inhale (pull, exhaust) • Exhale (push, supply)

  6. Two ways to dilute and remove contaminated air First choice: Single pass Re-circulation + HEPA filtration Rooms in a health facility

  7. Designs to provide air mixing Airflow patterns are affected by: • Air temperature • Location of furniture • Space configuration • Movement of health care workers (hcw) exhaust hcw supply hcw exhaust

  8. Short circuiting • Clean air is removed before it is mixed with room air • Contaminated air in the room is not effectively diluted or removed supply exhaust

  9. Negative pressure keeps droplet nuclei in the room • Air flows from a higher pressure area to a lower one • A room under negative pressure has a lower pressure than adjacent areas, so air is drawn into the room; negative pressure directs the airflow • Negative pressure is achieved by exhausting more air from a room than is supplied

  10. 225 m3/h 200 m3/h 200 m3/h 225 m3/h 135 m3/h 135 m3/h What is negative pressure? Nurse room (Positive) Patient room (Negative) 25 m3/h

  11. Negative pressure room • Air flows into room, from higher to lower pressure • 10% flow differential is minimum required • Keep doors and windows closed • Monitor to ensure negative pressure is maintained

  12. Negative pressure evaluation • Smoke tube • Pressure sensor • Flutter strips • Velocity meter

  13. Vaneometer

  14. TB transmission in a TB dispensary, Russia

  15. Checking airflow in the TB dispensary

  16. Exhaust ventilation

  17. Where does the air go?

  18. Where does the air go?

  19. Exhaust Supply

  20. Exhaust Supply

  21. B. Mixed mode ventilation • Combines the use of mechanical and natural ventilation • Is done through the installation of an exhaust fan to increase the rate of air changes in the room • Can be useful in places where • natural ventilation is not suitable (e.g. very cold weather) • fully mechanically ventilated rooms are not available

  22. Fans

  23. Window exhaust fan

  24. Airflow with window exhaust fan Window fan Patient room Corridor

  25. Window exhaust fan

  26. Where goes that air? Short-circuiting

  27. C. Regular cleaning and maintenance

  28. Routine monitoring, recording • The operation of ventilation systems should be regularly monitored • Is the air moving? Is it moving in the right direction? • Record performance and dates of all routine monitoring activities

  29. Smoke test to visualize air movement

  30. Maintenance and inspection of natural ventilation systems • Are the windows open? • Designate a person to routinely inspect • Record results

  31. Summary • Mechanical ventilation systems must be well-designed, maintained and operated • A room under negative pressure has a lower pressure than adjacent areas, so air is drawn into the room. This prevents infectious particles from escaping • Mixed mode ventilation systems combine the use of mechanical and natural ventilation

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