Operation and Calibration of Thermo-Hygrometer

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1. Purpose

To define the standard procedure for operation, monitoring, and calibration of thermo-hygrometers used for measuring temperature and relative humidity in pharmaceutical controlled areas, ensuring accuracy, reliability, and compliance with regulatory guidelines and GMP requirements.

2. Scope

• QC Laboratories
• Stability Storage Areas
• Warehouses and controlled storage areas

3. Responsibilities

Role	Responsibility
QC Analyst / User	Routine operation, monitoring, and recording of readings
QC Supervisor	Review monitoring logs and ensure compliance
Quality Assurance	Oversight, deviation handling, and audit readiness
Engineering / Calibration Personnel	Perform instrument calibration and maintenance

4. Equipment & Materials

• Digital Thermo-Hygrometer
• Reference Thermo-Hygrometer (ISO/IEC 17025 traceable)
• Humidity chamber / salt solution kit (for RH calibration)
• Authorized Log Sheets / Calibration Records
• Valid Calibration Certificates

5. Operation Procedure

• Check instrument for physical damage, clean sensor, and verify battery/power supply.
• Ensure instrument has a valid calibration and label attached.
• Place the thermo-hygrometer at a representative location in the controlled area, away from direct sunlight, doors, HVAC vents, or walls.
• Switch ON the device and allow stabilization for 10–15 minutes or as per manufacturer manual.
• Check display units: Temperature (°C) and Relative Humidity (%RH).
• Record readings on authorized log sheet:
• Date & Time
• Temperature (°C)
• Relative Humidity (%RH)
• Operator Name / Signature
• Monitor readings at defined frequency (continuous via data logger preferred, otherwise at least twice per shift).
• If readings are outside acceptable limits, immediately notify QC Supervisor and initiate corrective actions (adjust HVAC, relocate samples, etc.).
• Maintain log sheets as per GDP and audit requirements.

6. Calibration Procedure

6.1 Pre-Calibration Checks

• Inspect instrument for damage, cleanliness, and proper function.
• Ensure reference standard is valid, traceable, and within calibration due date.
• Allow both instruments to stabilize in controlled environment (30–60 minutes).
• Record instrument details: ID, serial number, model.

6.2 Calibration Frequency

• Routine: Every 6–12 months.
• After repair, battery replacement, or abnormal readings.

6.3 Calibration Method – Temperature

• Use controlled environment or reference thermometer.
• Measure at minimum three points: Low, Mid, High within operating range.
• Allow stabilization at each point for at least 5 minutes.
• Record readings and calculate deviation: Deviation = Instrument – Reference
• Deviation must be within ±2.0°C (or as per manufacturer manual).

6.4 Calibration Method – Relative Humidity

• Use humidity chamber or saturated salt solutions.
• Check at minimum three RH points: Low, Mid, High (30–75%).
• Equilibrate instrument for 20–30 minutes per point.
• Record RH readings and calculate deviation.
• Deviation must be within ±5% RH.

6.5 Post-Calibration Activities

• Affix calibration label with calibration date and next due date.
• Attach calibration certificate to instrument file.
• If any point fails, mark instrument as OUT OF CALIBRATION and remove from use.
• Notify QC Supervisor and QA, perform impact assessment and initiate deviation report.

7. Area-Specific Environmental Limits

Area	Temperature	Relative Humidity
QC Lab	20–25°C	40–60% RH
Stability Area	25±2 / 30±2 / 40±2°C	60±5 / 65±5 / 75±5%
Warehouse	15–30°C	≤65% RH

8. References

• WHO Technical Report Series – GMP
• ICH Q7, Q9, Q10
• USP <659> and USP <1079>
• EU GMP Guidelines – EudraLex Volume 4
• ISO 9001
• ISO/IEC 17025
• Manufacturer’s Instruction Manual (Thermo-Hygrometer)

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