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Swedish manufacturer of gas detection products for the refrigeration industry Samon AB has developed a manual providing an overview of when, how and why gas detection of refrigerant gases such as ammonia is required.

Aimed to persons involved with planning, installing and maintaining commercial and industrial refrigeration systems, the manual offers an overview of how the existing standards are implemented and what is required for different applications, including ammonia refrigeration.

Four main reasons to install gas detection systems

There are four main reasons to install gas detection systems:

• Personnel health & safety
• Environmental care
• Compliance with applicable rules and regulations
• Financial reasons

Regarding the third reason - complying with applicable rules and regulations – the guideline goes into discussing some of the most important regulations affecting ammonia technology at European level, such as the ATEX Directive concerning explosion-classified spaces and European standard EN378: 2008 requiring that systems with charges of more than 50 kg of ammonia must have a fixed gas detection system installed. It also outlines different aspects that need to be considered at the national level such as national legislation on gases, national legislation for occupational exposure limits as well as different rules pertaining to marine refrigeration.

Appropriate alarm levels for ammonia refrigerant

Samon AB recommends the following appropriate alarm levels for ammonia leakage alarms:

Pre-alarm	50-300 ppm
Leakage alarm	500-1000 ppm
Main alarm	> 3000 ppm

Measurement techniques for measuring or detecting gas

According to the manual, the most commonly used measurement systems for gas sensing are semiconductor sensors, electrochemical sensors, catalytic sensors and infrared measurement techniques. The systems have different advantages and disadvantages and differ substantially in cost:  

Methodology	Advantages	Disadvantages
Semiconductors	Stable zero point	Limited range
Electrochemical	Selectivity Medium purchase price	Short life (18-48 months) Short calibration interval Limited range High maintenance cost
Catalytic	Low purchase price	Short calibration interval
Infrared technology	High selectivity	High maintenance costs