Quick answer: For chicken eggs in a forced-air incubator, the usual settings are about 37.5 °C (99.5 °F) with 50–55 % RH for days 1–18, then about 65–75 % RH for the last three days of hatching (lockdown), with turning stopped. Still-air incubators run slightly warmer at egg height. Other species differ. Check temperature and humidity at egg level with a calibrated thermometer and hygrometer, monitor egg weight loss, and keep the incubator room itself at a steady temperature and humidity so the machine can hold its setpoints.
Quick answer (chicken, forced-air)
- Days 1–18: about 37.5 °C, 50–55 % RH, turning several times a day.
- Days 19–21 (hatch): about 37.0–37.5 °C, 65–75 % RH, no turning.
- Eggs typically lose about 11–13 % of their weight by day 18.
Settings by stage (chicken eggs)
| Stage | Temperature | RH | Turning | Ventilation |
|---|---|---|---|---|
| Setting, days 1–18 | about 37.5 °C (99.5 °F) forced-air | 50–55 % | Several times a day | Small, increasing with embryo growth |
| Hatching, days 19–21 | about 37.0–37.5 °C | 65–75 % | Stopped | Increased as chicks hatch |
Mississippi State University Extension summarises the key incubation factors, including temperature, humidity, ventilation and turning (MSU Extension). Follow the incubator maker's settings and species-specific guidance.
Why humidity matters
Humidity controls how much water an egg loses through its shell during incubation:
- Too dry: eggs lose too much water; chicks may be small, weak or stick to the membrane.
- Too humid: eggs lose too little water; chicks are large, wet ("mushy"), and may fail to pip.
Weight loss check: weigh a sample of eggs at setting and again around day 18. A loss of roughly 11–13 % indicates humidity is about right; adjust RH if the loss is consistently too high or low.
Measure at egg level
- Place a calibrated thermometer and hygrometer at the height and position of the eggs, not at the top of the cabinet.
- Check against a reference at least before each season; NIST describes hygrometer calibration (NIST).
- Wet-bulb thermometers are common in incubators: about 29–30 °C wet bulb at 37.5 °C dry bulb corresponds roughly to 55 % RH.
The incubator room
An incubator draws its air from the room. If the room is hot, cold, dry or humid, the machine struggles. Commercial hatcheries condition the supply air to the incubator and hatcher rooms:
| Room | Typical aim |
|---|---|
| Egg storage | Cool and humid (often around 15–18 °C and 75 % RH for short storage) |
| Setter (incubator) room | Stable temperature, about 24–27 °C, moderate humidity |
| Hatcher room | Higher ventilation; humidity supplied for hatching |
Humidity is usually added in hatcheries, especially in dry or cold climates where heated air is very dry. Our ultrasonic humidifiers (3 to 102 kg/h) are used to humidify supply air and rooms. In humid climates, dehumidification may be needed in egg storage or setter rooms to avoid condensation on cool eggs; see industrial dehumidifiers.
Alarms and records
- High and low temperature alarms (a few tenths of a degree matter).
- Humidity alarms.
- Turning failure and power failure alarms.
- A batch record: settings, readings, egg weight loss, hatch rate.
FAQ
Frequently asked questions
What humidity should an egg incubator be?
For chicken eggs, about 50–55 % RH for days 1–18 and 65–75 % RH for hatching.
What temperature should an incubator be for chicken eggs?
About 37.5 °C (99.5 °F) in forced-air incubators; still-air incubators run slightly warmer at egg height.
How do I know if incubator humidity is right?
Weigh eggs: about 11–13 % weight loss by day 18 indicates suitable humidity.
Why raise humidity at hatching?
To keep the membranes from drying out and sticking to the chicks while they hatch.
Sources
- Mississippi State University Extension, Important incubation factors.
- NIST, Hygrometers.
