Table 2.
Suggested CO2exposure time for euthanasia of rats of various ages
| Appearance of animal | CO2 exposure time (min) |
| Nonhaired pups (0 to 6 d of age) | 40 |
| Haired pups, eyes closed (7 to 13 d of age) | 20 |
| Haired pups, eyes open, preweaning (14 to 20 d of age) | 10 |
| Weanlings and adults (21 d of age and older) | 5 |
The sample exposure chart presented here applies to the exposure chamber and filling parameters used in this study. The use of other chamber types and fill rates will require separate calibration. All euthanasia times recommended in this table should be validated at each facility, using current equipment and animals.