Fire Cylinder

Welcome to Coltraco Ultrasonics’ range of portable Liquid Level Indicators.

We pride ourselves in our UK made, high-quality, reliable, and accurate instrumentation designed for fire suppression systems such as CO2, FM-200™, NOVEC™ 1230, Halons and a wide variety of other clean agents. 

We have been developing non-invasive level detection technology for over 30 years and are proud leaders in this field.

Coltraco Ultrasonics are global leaders in the monitoring of liquefied and non-liquefied gaseous extinguishing systems that protect high-asset value installations and critical national infrastructure.

Portagas® is a world’s first technology for non-invasive, non-destructive monitoring of pressurised, inert gas systems.

It is a unique and innovative solution designed to monitor the pressure of pressurized, non-liquefied inert gases and compressed gas cylinders, including Inergen®, Nitrogen, Oxygen, Propane, Methane, Chlorine, Ammonia, Hydrogen, and CO2.

Utilizing sophisticated signal processing and acoustic technology to detect even minor fluctuations in internal cylinder pressure, with precision below the 5% required by regulations and by detecting marginal changes in the internal cylinder pressure with precision well below 5% demanded by the regulations, making it a valuable tool for ensuring safety and compliance.

P/N: 3107505-GAS

Portalevel® MAX PLUS is our latest high-spec UL listed addition to our line of handheld, battery powered liquid level indicators. With Portalevel® MAX PLUS, an operator can rapidly and reliably detect the liquid level within a fire cylinder, with clear GAS / LIQUID interface, with an accuracy of ±1.5mm in under 30 seconds.

P/N: 2290334-COMXPS
NSN: 6625-99-257-8336
IMPA MSG P/N: 652776


Portalevel® MAX NIPPON is a handheld, battery powered liquid level indicator specifically designed to be used on the thicker-walled cylinders which are common in Japan. It comes with a sensor extension rod for testing banks of cylinders and Portalevel® MAX NIPPON is specially calibrated as a solution for cylinders commonly used in the Japanese fire sector.

P/N: 2290334-COMX-NIP


The Portalevel® ORIGINAL is our low-cost, portable and battery powered, liquid level indicator designed to non-invasively, accurately, and reliably measure the level of fire suppression agent contained within a cylinder. The Portalevel® is suitable for most standard size cylinders containing CO2, Liquified Clean Agents and Halons.

P/N: 2290334-OR

The Portalevel® MINI is a portable and battery powered, liquid level indicator designed to non-invasively, accurately, and reliably measure the level of fire suppression agent contained within a cylinder. The Portalevel® MINI is suitable for most standard size cylinders containing CO2, Liquified Clean Agents and Halons.

P/N: 2290334-MINI

The Portalevel® INTRINSICALLY SAFE is an ultrasonic liquid level indicator approved for Zone 1 ATEX hazardous or explosive environments.

P/N: 2290334-IS

The Portasteele® CALCULATOR is the perfect partner to any of Coltraco Ultrasonics’ liquid level detectors. It allows you to convert your measured liquid level to an agent weight, precisely and accurately. These readings can then be saved and exported for future reference and traceability. 

Used in partnership with the Portalevel® Ultrasonic Level Indicator range 

P/N: CALC-007

Why choose Coltraco Ultrasonics’ range of Ultrasonic Liquid Level Indicators?

Using ultrasonic technology to check the contents of your fire suppression cylinders is non-invasive, non-destructive and non-disruptive meaning it is safer for personal and does not require the user to shut down the fire suppression system during inspection. The use of ultrasonic technology is a regulatory approved alternative method for monitoring the contents of cylinders. Our range of ultrasonic liquid level indicators are accurate to ±1.5 mm.

The non-disruptive, non-invasive nature of ultrasound contents monitoring in-situ and operational. This process takes around 30-seconds per cylinder using our easy-to-use, intuitive technology. Compare this to traditional, manual weighing which requires lifting equipment, multiple people and around 15-minutes for inspection.

Cheaper; Enabling inspection to take place without disruption your cylinder installation means no shut-down, saving time and no requirement for multiple operators, saving labour costs. We have a large range of level monitoring technology allowing us to be competitive with pricing and Coltraco Ultrasonics have a “Price Promise” to be the most competitive on the market

What are fire suppression systems and why do we monitor them?

Fire suppression systems consist of a group of fire cylinders, either welded seam, or seamless depending on the pressure and are integral for protecting vital infrastructure, people and assets from damage due to fire. Fire suppression systems are used to extinguish, control and prevent fires from spreading. These systems are used in a vast variety of applications in multiple sectors and environments all with unique requirements and challenges associated with the installation.

The standard configuration of a fixed fire suppression system includes a bank of high-pressure cylinders. These cylinders contain a fixed quantity of fire suppression agent used to extinguish a fire and is controlled by a centralised fire panel and actuating system. We specialise in the monitoring of all types of liquified fire suppression agents, but the most common types are CO2, FM-200™, NOVEC™ 1230 and Halons.

In the event a fire is detected the centralised monitoring system, which usually consists of heat and smoke detectors trigger the alert system and activates the fire suppression system. The cylinder valves are opened, and the pressure of the cylinders drive the agent through a pipe network to be discharged at the point of fire. In some cases, these systems are supported by ancillary nitrogen cylinders if the distance the agent needs to travel is great.

Fire suppression systems, especially high-pressure cylinders can leak and fail over time. Regulations state that storage container contents must be checked at least every six months, which ensures that the system is fully operational and contains the correct volume of agent sufficient to suppress a fire.

ISO 14520-1:2015 (Gaseous fire-extinguishing systems – Physical properties and system design – Part 1: General requirements)

Chapter 9.2 Inspection, 9.2.1 General The storage container contents shall be checked every 6 months as follows:

Liquefied gases: for halocarbon agents, if a container shows a loss of agent in quantity of more than 5% or a loss of pressure (adjusted for temperature) of more than 10%, it shall be refilled or replaced

Annex F – System Performance Verification

Every 6 months: perform the following checks and inspections:

for liquefied gases, check the weight or use a liquid level indicator to verify the correct content of containers; replace or refill any showing a loss of more than 5%

Ultrasound & Ultrasonic Liquid Level Operating Principle

All of our liquid level indicators use ultrasonic sensors to identify the contents of fire suppression cylinders. Ultrasonic sensor technology or Ultrasonic Testing (UT) is a reliable, versatile and safe method for Non-Destructive-Testing (NDT). Ultrasonic waves are sound waves with frequencies above the upper limit of human hearing (above 20 kHz, or 20,000 Hz). Sound waves are mechanical waves that travel in a straight line and require a medium through which to travel. The propagation and attenuation of sound waves depend on the structure of the medium down to an atomic level; therefore, ultrasound is a useful method of studying a material’s structure and the processes occurring within it.

Whilst the highest frequency a human can hear is around 20,000 Hz, Our Portalevel® units are high-frequency ultrasound transmitters that use sound at a frequency of 1,000,000 Hz or 1 MHz. To do this, the main unit sends a strong electrical signal to the sensor (a piezoelectric crystal), which then emits a high energy pulse of ultrasound into the fire cylinder wall through what is known as the reverse piezoelectric effect.

The term ‘piezoelectricity’ has its roots in the Greek word ‘piezein’ (to press) and was discovered in 1880 by Pierre and Paul-Jacques Curie. Piezoelectricity is the appearance of an electrical potential across a crystal when it is subjected to mechanical stress and is a reversible effect. A crystal that exhibits this effect by becoming charged when it is compressed, or distorted is a piezoelectric crystal. Similarly, passing electricity through a piezoelectric crystal causes the crystal to vibrate back and forth (producing ultrasound); this is the reverse piezoelectric effect.

The ultrasound that is produced is conducted through the solid walls of the container and then interacts with the contents (CO2, FM™-200, NOVEC™1230, etc.). After the sensor, also known as an ultrasound transducer, stops emitting ultrasound, it starts listening for the returning echoes of the signal. It sends these signals back to the main electronic unit, which then analyses the returning signal in comparison to the calibration signal taken for each cylinder. This allows Coltraco’ range of liquid level indicators to detect the presence or absence of liquid behind the area of the container wall where the sensor is placed without disturbing the contents.

Portable Ultrasonic Liquid Level Indicator Range

Ultrasound interacts differently depending on the transducer and crystal. The diagram on the left (above) shows bulk waves in gas travelling radially inwards from the walls of a fire cylinder. Displacement is in the direction of propagation. The diagram on the right represents shear waves propagating radially over the surface of the cylinder from the point of the transducer contact. Displacement, in this case, is perpendicular to the direction of propagation. This information along with advanced signal analysis and calibration algorithms provide us with a clear picture of contents inside the cylinder and allows us to differentiate between the liquid and gas section.

History of Ultrasonic Level Measurement

Coltraco was founded in 1987 by father and son, Mr E C Hunter and Mr Carl Stephen Patrick Hunter OBE (current chairman). Mr E C Hunter served in the Royal Navy’s Submarine service for 27 years, as well as 5 years spent working for the Admiralty Research Laboratories, where he specialised in SONAR (SOund-Navigation And Ranging) technologies. His experiences allowed him to notice the need for a portable ultrasonic technology, which would enable the user to measure and monitor the contents of marine CO2 fire suppression systems. Technology at the time typically involved the weighing of gas cylinders or using radioactive sources, neither being convenient nor safe to use. In 1987 Mr E C Hunter was able to release the ‘world’s first dedicated marine portable liquid level indicator.’ It was then possible for users to find the liquid level within liquified gas bottles, without either disrupting the system or using cumbersome techniques.

Throughout the years and decades, Coltraco Ultrasonics have continued to improve the Portalevel system, while expanding into the development of more products and systems; a large number of these use ultrasound to either test the integrity of a system or to measure the contents within. The Portalevel is used mainly in the Fire and Safety industry but is now used extensively in over 25 market sectors. The development of an ultrasonic liquid level indicator unit allowed for the replacement of old methods, since radioactive liquid level devices have become more and more expensive, and weighing heavy fire suppression cylinders requires a lot of time and is labour intensive.

What does the Portalevel® range do?

The Portalevel® range is designed to be a portable way to non-invasively locate the liquid level inside any single skinned cylinder welded or seamless fire suppression cylinder. Each Portalevel® unit is capable of detecting the presence of liquid externally; from water and liquid pressurised gases to clean agents and halons. The Portalevel® range can be used on an extensive range of container types, composed of different materials, shapes and sizes, but are typically most used on steel high-pressure compressed gas cylinders.

Our technology is suitable for many applications, but it is most widely used as a replacement to both weighing fire suppression cylinders during installation and servicing, or replacement for the fitting of internal and invasive liquid level ‘float’ devices. Once the liquid level height inside a container has been located, the agent weight can be determined using the Portasteele®Calculator, which is designed to quickly convert liquid height to weight accounting for the cylinder size, agent type and temperature (see below). 

Inspections can take a little as 30 seconds for each bottle and displays easy to understand results indicating the presence of liquid or gas. This ultrasonic level sensing technology is suitable for other liquid level monitoring applications, including LPG gas level indication and in non-fire suppression containers such as water level measurements. Please, visit our case studies page or contact us to find out more.

Converting Liquid Level to Weight

Monitoring the liquid level in fire cylinders is a vital aspect of any fire suppression system maintenance schedule, however, understanding how the liquid level relates to the fill weight of the cylinder is equally important. Coltraco Ultrasonics offer, in conjunction with the Portalevel® range, the world’s first liquid level to agent mass calculator. 

The Portasteele® Calculator calculates the agent weight of a fire suppression cylinder. It does this by using the liquid level determined by our Portalevel® range or inversely, by using the required fill level for a certain weight of suppression agent. The Portasteele® Calculator is sold as a stand-alone unit on a 7’’ hand-held tablet to be used in conjunction with our Portalevel® range.

Fire Cylinder and Fire Suppression System Frequently Asked Questions

What are the different types of fire cylinders?

There are various types of fire cylinders used for storing firefighting agents. Some common types include carbon dioxide (CO2) cylinders, dry chemical powder cylinders, foam solution cylinders, and water cylinders. Each type of cylinder is specifically designed to contain and discharge the appropriate firefighting agent for extinguishing different types of fires.

What are the 2 types of fire systems?

The two main types of fire systems are automatic fire detection and alarm systems and automatic fire suppression systems. Automatic fire detection and alarm systems detect signs of fire, such as smoke or heat, and provide early warning through audible and visual alarms. Automatic fire suppression systems, on the other hand, are designed to automatically suppress or extinguish fires using substances like water, foam, gas, or dry chemical agents.

What are the 5 different classes of fire?

The five different classes of fire are Class A, Class B, Class C, Class D, and Class K:

  • Class A fires involve common combustible materials such as wood, paper, fabric, and plastics.
  • Class B fires involve flammable liquids and gases, such as gasoline, oil, propane, and solvents.
  • Class C fires involve energized electrical equipment or wiring.
  • Class D fires involve combustible metals like magnesium, titanium, or potassium.
  • Class K fires involve cooking oils and fats typically found in commercial kitchens.
What is the difference between L1 and L2 fire systems?

L1 and L2 fire systems refer to different levels of fire alarm and detection systems. The key difference lies in the extent of coverage they provide within a building. An L1 fire system provides the highest level of coverage, with detectors placed throughout the entire building, including all areas and compartments. An L2 fire system, on the other hand, provides coverage in selected areas, typically focusing on escape routes, high-risk areas, and key locations.

What is the most common fire system?

The most common fire system is the automatic fire detection and alarm system. This system includes smoke detectors, heat detectors, or a combination of both, along with audible and visual alarms. It is widely used in various buildings, including residential, commercial, and industrial settings, to provide early warning of fire and initiate appropriate evacuation and firefighting procedures.

What are the different levels of fire systems?

The different levels of fire systems typically refer to the categories outlined by local fire codes and regulations. The specific terminology and categorization may vary, but commonly used levels include Level 1, Level 2, Level 3, and so on. These levels generally indicate the extent of coverage, sophistication of the system, and compliance with fire safety standards.

What is the standard fire classification in the UK?

In the UK, the standard fire classification system uses letters to categorize different classes of fires. The standard fire classification in the UK includes Class A, Class B, Class C, Class D, and Class F. The classifications are similar to the ones mentioned earlier, where Class A refers to fires involving solid combustible materials, Class B involves flammable liquids or gases, Class C involves electrical fires, Class D involves fires with combustible metals, and Class F involves fires related to cooking oils and fats.

What are the 7 types of fire extinguishers?
  • The seven types of fire extinguishers are:
  • Water extinguishers (Class A fires)
  • Foam extinguishers (Class A and Class B fires)
  • Powder extinguishers (Class A, B, C fires)
  • Carbon dioxide (CO2) extinguishers (Class B and Class C fires)
  • Wet chemical extinguishers (Class F fires, specifically for cooking oil/fat fires)
  • Clean agent extinguishers (Class A, B, C fires)
  • Dry chemical extinguishers (Class A, B, C fires)

These different types of fire extinguishers are designed to tackle specific classes of fires based on the fuel involved. It is important to choose the appropriate type of extinguisher for the specific fire hazard to effectively suppress the fire and minimize risks.