Source of Fresh Air | Environment | ||||||||
Airplanes | Trains | Hospital Delivery & Operating Rooms | Office Buildings | School Classroom* | Typical School Classroom | Typical Home | |||
| | | | | | | |||
Typical Occupancy Level | |||||||||
High | High | Medium | Medium | Medium/High | Medium/High | Low/Medium | |||
Typical Air Changes per Hour (ACH) | |||||||||
Ventilation (Displaced Air Indoors, with Air from Outdoors) | 10 - 15 | 8 | 5 | 1 - 2.5 | 6 - 10 | 4 - 6 | 0.25 | ||
HEPA Air Filtration | 10 - 15 | 6 | 20 | 3 - 7.5 | 0 | 0 | 0 | ||
Combined (Ventilation + HEPA Air Filtration) | 20 - 30 | 14 | 25 | 4 - 10 | 6 - 10 | 4 - 6 | 0.25 | ||