Climate Control SOP — Temperature, Humidity, CO₂ and Airflow — India Setup Procedure & Equipment Cost

Step-by-step procedure

1. 1. Establish the design basis before buying machinery

   Size the plant on peak ambient for your district, not on the annual average. The heat load is the sum of transmission through the PUF envelope, fresh-air load, the crop's own respiration heat, lighting, people and door openings. Under-sizing shows up only in May and June — exactly when the market price is highest — so the buffer belongs in the design, not in the operating manual.

   • Sized on district peak ambient
   • Crop respiration heat included in the load
   • Starting-surge buffer included in DG sizing

2. 2. Build a sealed, insulated envelope

   Climate control is impossible in a leaky room. Specify PUF panels with PPGL coating on walls and roof, sealed panel joints, insulated doors with functioning gaskets, sealed cable and pipe penetrations, and drain traps that hold water. A room that leaks air also leaks spores and flies in the opposite direction.

   • All joints sealed
   • Door gaskets intact
   • Drain traps water-filled at all times

3. 3. Install air distribution for 7-tier uniformity

   Deliver conditioned air through overhead ducting with adjustable outlets so air is thrown along the length of the room and returns through the rack spaces. The design target is uniform velocity across every tier without blowing directly onto the beds, which dries caps and causes scaling. Commission the ducting by measuring velocity at the first, middle and last outlet and balancing the dampers.

   • Velocity variation between outlets under 15%
   • No direct airflow onto bed surfaces

4. 4. Set up sensors and the controller

   Install air temperature, compost temperature, RH and CO₂ sensors per room, with compost probes at three tiers. Set the controller to stage-based recipes rather than manual setpoints, so an operator changing a shift does not change the crop. Log at four-hour intervals minimum; hourly is better and costs nothing once a datalogger is installed.

   • Compost probes at 3 tiers
   • CO₂ sensor per room
   • Automatic logging enabled

5. 5. Run the spawn run climate stage

   Air 22–24 °C, RH 90–95%, CO₂ 5,000–15,000 ppm, fresh air near zero. Track compost temperature, not air temperature, as the controlling variable, because the crop's self-heating of 2–3 °C is what actually determines whether the mycelium is stressed. Lower the air setpoint progressively from Day 4 as the heat load builds.

   • Compost 24–25 °C, never above 28 °C
   • Fresh air minimal

6. 6. Run the case run climate stage

   Air 24–25 °C, RH 92–95%, CO₂ 5,000–10,000 ppm. Humidity is the priority here: the casing layer must never dry, and the humidifier should be running in short frequent cycles rather than long ones, which cause wet surfaces and blotch.

   • RH 92–95% held continuously
   • Short humidifier cycles

7. 7. Execute the airing-down ramp

   Move from case run to cropping over 24–48 hours: air 24 °C to 17–18 °C, CO₂ from above 5,000 ppm to below 1,000 ppm, RH to 88–92%. Fresh-air requirement rises sharply here to roughly 5–8 m³/hour per square metre of bed. This is the peak simultaneous demand on both the refrigeration and the fresh-air system, and it is the load case that should have sized the plant.

   • Controlled ramp, not a step change
   • CO₂ under 1,000 ppm at the end of the ramp

8. 8. Hold the cropping stage and manage flushes

   Air 16–18 °C, RH 85–90%, CO₂ under 1,000 ppm during flushes. CO₂ and respiration heat peak with each flush and fall between flushes, so the fresh-air fraction should follow the crop rather than sit at a fixed value. Between flushes, RH can be held slightly higher to help the casing recover after watering.

   • Air 16–18 °C ±1 °C across all tiers
   • CO₂ under 1,000 ppm during flush

9. 9. Weekly maintenance and calibration

   Clean AHU filters weekly, check condensate drainage, verify refrigerant pressures monthly, calibrate CO₂ sensors quarterly against a reference meter, and verify temperature probes against a calibrated thermometer monthly. A drifting CO₂ sensor is the most common invisible cause of a poor pin set, because the controller believes the room is aired when it is not.

   • Weekly filter clean
   • Monthly probe verification
   • Quarterly CO₂ calibration

Daily and per-cycle routine

• Read and log air temperature, compost temperature, RH and CO₂ every four hours in every room.
• Walk each room daily and confirm the controller reading against a handheld meter at the far tier.
• Clean AHU filters weekly and record the date on the unit.
• Check condensate trays and drain traps weekly for blockage and standing water.
• Verify temperature probes monthly and CO₂ sensors quarterly against a reference instrument.
• Record every setpoint change with the reason, the operator and the timestamp — unexplained setpoint drift is a common cause of crop variability.
• Log DG run hours and any power interruption longer than 15 minutes against the affected rooms.

Troubleshooting

How this SOP fits mushroom farming setup in India

Frequently asked questions