In most home canning recipes, recommended processing times for boiling water and pressure canners are stated for use at elevations of 0 (sea level) to 1,000 ft (305 m). Because air is thinner at higher elevations, water boils at temperatures lower than 212°F (100°C) and pressure levels are reached at lower temperatures. Lower temperatures are less effective in destroying microorganisms, so adjustments must be made to assure the safety of home canned foods preserved at higher altitudes.
When using a boiling water canner at altitudes higher than 1,000 ft (305 m), processing times must be extended.
Boiling Water Canner- Altitude Adjustments
| ALTITUDE (FEET) | ALTITUDE (METERS) | INCREASE Processing Time |
| 1,001 - 3,000 | 306 - 915 | 5 minutes |
| 3,001 - 6,000 | 916 - 1,830 | 10 minutes |
| 6,001 - 8,000 | 1,831 - 2,440 | 15 minutes |
| 8,000 - 10,000 | 2,441 - 3,050 | 20 minutes |
