Guardian of Cold Chain Safety: Comprehensive Gas Monitoring Solutions for the Rapid Freezing and Cold Storage Industry

In the modern food industry, rapid freezing and cold storage technology is essential to ensure that meat, aquatic products, and agricultural goods remain fresh from origin to table. However, as the “lifeblood” of refrigeration systems, liquid ammonia, Freon, and liquid nitrogen used for ultra-low temperature freezing not only provide cooling but also conceal significant safety risks.

Once refrigeration pipelines corrode, age, or suffer physical impact leading to leakage, it can result in costly cargo loss, poisoning, chemical burns, or even explosion accidents. Nexisense focuses on gas sensing technology in the refrigeration industry, using intelligent monitoring systems to confine invisible refrigerant leakage risks within a “safe cage.”

Hidden Risks Beneath the Ice: Key Gases Monitored in the Rapid Freezing and Cold Storage Industry

1. Liquid Ammonia (NH3): Efficient but Dangerous Refrigerant

Liquid ammonia is widely used in large and medium-sized cold storage facilities due to its high refrigeration efficiency and low cost. However, ammonia gas is highly irritating and corrosive.

• Health Hazards: Even extremely low concentrations can irritate the respiratory tract; high concentrations may cause pulmonary edema, suffocation, or death.

• Physical Injury: Skin contact can cause severe chemical burns and frostbite.

• Explosion Risk: The explosive range of ammonia in air is 15% - 28%. In enclosed spaces, it can easily trigger secondary disasters.

2. Freon: Invisible Greenhouse Effect and Asphyxiation Risk

Small and medium-sized cold storage facilities commonly use R22, R134a, R404A, and other Freons. Although colorless and odorless, large leaks can displace oxygen inside the chamber, causing unconscious suffocation. They also contribute to ozone layer depletion.

3. Liquid Nitrogen (LN2): Oxygen-Deficiency Hazard in Ultra-Fast Freezing

During operation or discharge of liquid nitrogen quick-freezing machines, large amounts of nitrogen rapidly dilute oxygen levels in localized spaces. If ventilation is inadequate and oxygen concentration falls below 19% Vol, workers face life-threatening risks.

Nexisense Product Matrix for Rapid Freezing and Cold Storage: Multi-Dimensional Safety Protection

To address high humidity, low temperature, and enclosed environmental conditions, Nexisense has developed a closed-loop monitoring system ranging from fixed online detection to portable inspection devices.

Fixed Sentinel: SGA-500 Series Online Liquid Ammonia / Refrigerant Detector

This is the core monitoring device for machine rooms and cold chambers:

• Original imported sensors: Equipped with high-precision electrochemical or infrared sensors, offering excellent repeatability and a service life of 3–5 years.

• Low-temperature resistant design: Specially compensated circuitry ensures stable operation in -40°C cold storage environments without data drift caused by extreme cold.

• Intelligent linkage interface: Built-in relay outputs can directly activate spray systems (to absorb ammonia), forced ventilation fans (to dilute concentration), or cut off solenoid valves (to isolate leak sources).

Inspection Tool: SGA-600 Series Portable Liquid Ammonia Detector

Ideal for equipment maintenance and routine inspections:

• Multiple sampling modes: Includes diffusion type (wearable), pump-suction type (remote sampling), and probe type (deep-gap detection).

• High-decibel alarm: Ensures operators clearly hear alarms even amid the high background noise of refrigeration equipment.

Central Brain: SGA-800 Series Gas Alarm Controller

Installed in cold storage monitoring rooms or security offices:

• Multi-point aggregation: Real-time display of concentration values across warehouses and machine rooms.

• Black box recording: Automatically stores alarm records for accident tracing and compliance auditing.

Intelligent Linkage: Nexisense Emergency Response Logic

In the rapid freezing and cold storage industry, merely issuing an “alarm” is not enough. Rapid emergency response is key to minimizing losses. Through the SGA-500, Nexisense implements a three-level linkage mechanism:

1. Pre-warning Level (Low Alarm): When ammonia concentration reaches 25ppm, the system automatically activates ventilation to dilute the gas and notifies the control room to inspect pipelines.

2. Mandatory Level (High Alarm): When concentration exceeds 50ppm, the system automatically triggers the spray system. Taking advantage of ammonia’s high solubility in water, the water mist physically absorbs ammonia to reduce airborne toxicity, while simultaneously cutting off the main refrigeration pump power.

3. Personnel Protection Level: On-site audible and visual alarms are fully activated, instructing personnel to evacuate according to predefined emergency routes.

Why Cold Chain Leaders Choose Nexisense

1. High-humidity condensation resistance: Probe heads are treated with conformal coating and hydrophobic structural design to effectively prevent moisture-induced short circuits caused by frequent door opening and condensation.

2. Rapid response capability: For sudden ammonia leaks, the sensor features a T90 response time of less than 20 seconds, significantly faster than industry averages.

3. Regulatory compliance: Complies with cold storage design and ammonia refrigeration safety standards, supporting fire protection inspection and official acceptance.

4. Low maintenance cost: Supports intelligent modular replacement without requiring professional technicians to perform gas calibration.

In-Depth Analysis & Frequently Asked Questions (FAQ)

Q1: Cold storage environments typically range from -20°C to -40°C. Ordinary sensors may fail due to freezing. How does Nexisense solve this?

A1: Extreme cold is a major challenge for electrochemical sensors, as low temperatures can cause electrolyte crystallization and loss of responsiveness. Nexisense adopts dual low-temperature protection. First, the SGA-500 can be equipped with an internal constant-temperature heating module that maintains the sensor chamber above 5°C. Second, the imported low-temperature-resistant sensor uses special anti-freeze electrolytes that remain physically active even at -40°C, ensuring instant and accurate data output during sudden leaks.

Q2: Ammonia (NH3) is highly corrosive. How can the detector withstand long-term exposure?

A2: When ammonia encounters moisture, it forms alkaline ammonia water, which can corrode circuit boards and metal components. Nexisense addresses this with a dedicated protection system: high-grade anti-corrosion polymer coating on the transmitter housing; nano-level conformal coating on internal PCBs; 316L stainless steel probe housing; and a hydrophobic polymer filter membrane that allows rapid ammonia diffusion while blocking liquid ammonia water from entering the sensor, extending service life by 2–3 years.

Q3: Why should machine rooms install both low-range and high-range ammonia detectors?

A3: This ensures dual protection for personnel safety and explosion prevention.

• Low range (0–100ppm): Detects minor leaks. Ammonia begins to irritate humans at around 25ppm, making this range ideal for early detection.

• High range (0–1000ppm or 0–100% LEL): Used for explosion monitoring. In case of major rupture, it provides critical data and triggers valve shutoff before reaching the lower explosive limit. Nexisense supports integrating different ranges of SGA-500 within the same system for tiered alarm management.

Q4: Frequent door opening causes heavy condensation. How can false alarms and inlet blockage be prevented?

A4: Sudden temperature differences may cause condensation on sensor surfaces, obstructing gas diffusion. Nexisense adopts an “asymmetric ventilation balance” probe structure combined with a PTFE hydrophobic membrane. This material prevents water droplets from forming continuous films while allowing gas molecules to pass. Additionally, signal filtering algorithms eliminate interference caused by rapid humidity changes, ensuring alarm accuracy.

Q5: What is the spray linkage logic after the SGA-500 alarm is triggered?

A5: Since ammonia is highly soluble in water, water curtains are an effective physical absorption method.

• Level 1 linkage (low concentration): Activate ventilation via controller relay output.

• Level 2 linkage (high concentration): Trigger solenoid valve to activate automatic spray.

• Physical logic: Spray systems should be installed above potential leak sources such as compressors or valve groups. When high concentration is detected, water mist rapidly dissolves airborne ammonia, preventing gas clouds from spreading.

Q6: How should portable detectors be configured for cold chain logistics vehicles?

A6: The highest risk occurs when drivers open cargo doors. Nexisense recommends the SGA-600 pump-suction detector with one-key self-test. Before opening doors, operators insert the sampling probe through door seals to test internal air. If refrigerant accumulates, the 95dB alarm immediately alerts personnel to ventilate before entering, preventing suffocation or poisoning.

Q7: If the machine room uses CO2 refrigerant in addition to ammonia, can both be monitored simultaneously?

A7: Yes. With the growing adoption of CO2 refrigeration, Nexisense offers multi-gas solutions. The SGA-500 cluster system can simultaneously monitor NH3, CO2, and O2. CO2 uses NDIR infrared sensing technology, ensuring high selectivity without interference from ammonia or cleaning agents.

Q8: How can companies meet regulatory inspections from safety and fire authorities?

A8: Regulations require ammonia refrigeration machine rooms to install ammonia concentration alarms. Nexisense devices are delivered with metrology verification reports and explosion-proof certificates. The system supports one-click data export, providing complete alarm history and operation curves for compliance audits and safety traceability.

Conclusion

Gas monitoring in the rapid freezing and cold storage industry is a technological battle against “low temperature, humidity, and toxicity.” With exceptional cold resistance and advanced intelligent linkage logic, the Nexisense SGA series builds an invisible safety firewall for every stage of the cold chain.

Has your cold storage system passed the latest safety compliance inspection? Contact Nexisense professional engineers for one-on-one technical consultation, from machine room layout planning to automated spray linkage configuration—ensuring your cold chain operations achieve both safety and cost efficiency.