Bacteria are always present on food in small numbers. What decides whether they stay harmless or multiply into a hazard is mostly temperature and time. Between 40°F and 140°F — the range food-safety agencies call the danger zone — many common foodborne bacteria grow fast. Drag the thermometer and watch a starting population of 1,000 explode, or crawl.
Drag the thermometer
Holding temperature70°F
Drag the mercury or the slider. Freezer on the left, stove on the right.
The danger zoneset a temperature to begin
Time held out4hr
Doubling time
—
Bacteria now
1,000
from 1,000
Multiplied
×1
The colony (each dot ≈ a log-scale cluster)
Growth rate across temperature
Times and temperatures are typical, illustrative values. Real food safety depends on the food, the organism, and the conditions.