E.P.A. | ||||
| Environment | Normal | Contaminated Outside Dusty |
Extremely Cold Weather Climates |
High Humidity Biogenic |
| Day Care Center | 2 weeks | 1 week | 2 weeks | 1 week |
| Nursing Homes | 1 month | 1 month | 1 month | 1 week |
| Residence with: | ||||
| 2 persons, non-smoking | 6-12 months | 2 months | 4-6 months | 4-6 months |
| 2 persons, with smoking | 4 months | 2 months | 2 months | 4 months |
| young children | 6 months | 1 month | 2 months | 3 months |
| young children w/pets | 3-6 months | 1 month | 2 months | 2 months |
| Office Building: | ||||
| ground floor | 3-6 months | 1-4 months | 2-6 months | 2-6 months |
| higher floors | 6-12 months | 2-6 months | 3-9 months | 3-9 months |
| Food Service Establishments: |
1 month | 1 week | 2 weeks | 2 weeks |
| Commercial (retail shops, banks, etc.) |
3-6 months | 1 month | 2 months | 2 months |
** from a U.S. EPA letter in January 1989 by Dr Michael Berry.