Appendix 25. Overview of ventilation techniques

Natural 

Windows and doors 

Very simple 

Low 

• Adapted to hot climates only.  
• No constant airflow speed and direction.  

Whirly birds 

Very simple 

Low 

Assisted natural 

Fans (ceiling, wall, desk) 

Very simple 

Low 

• Adapted to hot climates only.  
• Improves dilution.  
• Power source required. 

Extractors/ exhaust fans 

Simple 

Low 

• Adapted to hot climates only.  
• Power source required. 

Mechanical 

Heating, ventilation and air conditioning 

Very difficult 

(requires specialised technicians) 

Very  

high 

• Adapted to cold and hot climates.  
• Constant airflow speed and direction if functioning properly.  
• Power source required (high consumption). 
• HEPA filters if air is recirculated.