JOB Thermo Bulbs

Sprinkler Glass Ampoules

Product description

JOB THERMO BULBS are thermal trigger elements for automatic sprinklers, smoke extractors and other trigger devices. A hermetically sealed liquid (type G or F) expands as the temperature in the glass bulb increases, so that the internal pressure in the ampoule increases until the ampoule bursts into tiny fragments at a defined trigger temperature

The unique bone shape of the JOB THERMO BULBS (US Patent No. 4,796,710 and other international patents) in combination with our special fluid (F-Type; US Patent No. 4,938,294) are crucial for the excellent thermal response and the strength of the glass bulbs. All essential features of the JOB THERMO BULBS can be found in the table below. If you have any questions, please contact the Thermo Bulbs contact, Jürgen Teschner.


JOB Thermo Bulbs in use worldwide

Application examples

St. Mark’s Basilica, Venice

St. Mark’s Basilica in Venice was the central state shrine of the Republic of Venice until its end in 1797. For many years, this special religious site has been protected by sprinkler systems equipped with JOB Thermo Bulbs.

Empire State Building

Empire State Building, New York

With a structural height of 381 meters and an antenna peak of 62 meters, the Empire State Building is not only one of the largest skyscrapers in the Manhattan district of New York City, but also certainly one of the most famous buildings in the world. The Empire State Building is also equipped with sprinkler systems that use JOB Thermo Bulbs.

Queen Mary

Cruise ships

There are approximately 385 cruise ships (> 49 passengers) worldwide. A fire on a ship is one of the most dangerous scenarios on the high seas. That’s why all these ships are equipped with sprinkler systems and all of these cruise ships use JOB Thermo Bulbs, made in Germany. Here in the picture, the Queen Mary 2 (QM2 key data: 2,691 guests, 1,173 crew, 345m length). JOB Thermo Bulbs are also used on the QM2.

JOB Thermo Bulbs – the original!

The Thermo Bulb, with its unique bone-shaped design, uses reinforced ends to optimally absorb forces and direct them axially into a reduced diameter shaft. This avoids unfavourable shearing and bending stresses in the glass. Specially designed tensions enable high strength and special filling fluids ensure very fast release times. These excellent properties have helped JOB establish itself as a global leader in the development, manufacture, and distribution of glass ampoules.


F3-SP Thermo Bulbs

F3 SP blau gold Logo

The Thermo Bulb Type F3-SP -superior- is a “Heavy Duty Fast Response” glass bulb with an approx. 50% higher resistance to lateral loads with the same response time index of 32 (ms)½, [58 (fts)½,] like our proven Thermo Bulb type F3.

F3-F – Thermo Bulbs

The Type F3-F Super-Fast Thermo Bulb is a high performance, fast-response ampoule with improved strength and response sensitivity properties. The triggering speed is 25% faster than the standard ampoule type F3/F3-SP with increased strength properties.

F3-XS Thermo Bulbs

XS stands for EXTRA STRENGTH. Thanks to a special manufacturing process, these glass ampoules have an axial strength that is approximately 30% higher than standard ampoules, thus ensuring high safety factors for special applications. These extra strong glass barrels are available in G5, F3 and F2.5

The latest generation of glass ampoules

The latest developments in the sprinkler industry require ever faster triggering speeds and very high strength properties of the glass ampoules. The JOB development team of technicians and engineers from various areas were put together to continuously improve the quality and properties of JOB Thermo Bulbs, and to meet the demand for the highest quality and technological leadership for life-saving products.

The smallest & fastest

The ultra-fast F2 and F1.5 ampoules are unique in the world. They are unique JOB creations with a release speed of just 19 or 14 milliseconds. The ultra-fast ampoules are just 16 millimetres in size.

F2 Ampulle

F1,5 Ampulle – smaller and even faster

Thermo Bulbs in action

Smart Bulbs in action

JOB Smart Bulb

A glass ampoule with two-way activation

The latest innovation from the JOB Group is an ampoule with two-way activation. The ampoule can be triggered thermally and electrically. There is the possibility of electrical monitoring to directly identify which glass ampoule triggered, when, and where.

Thermo Bulbs get smart!

  • Bonding directly on the ampoule
    • Sprinkler/system potential-free
    • Simple sprinkler installation
    • Flex conductor path from the automotive industry
  • Intelligent sprinkler system
    • Surveillance for each individual sprinkler
      Targeted activation of sprinklers
  • Additional sensor technology on the ampoule possible
    • Temperature measurement

Advantages of smart sprinklers

  • Reducing water storage
  • Flexible effective surfaces
  • Additional sensors on the sprinkler (e.g. temperature profile, …)
  • Networking with fire alarm technology
  • Effective firefighting through targeted activation of sprinklers
  • Reducing fire damage
  • Always backup function through thermal triggering

Response Time Index (RTI) -> Responsiveness

The Response Time Index is a calculated number that describes the actual response time of a glass vial in a sprinkler, or other device, under standard conditions. The RTI is an indication of the thermal responsiveness of the glass ampoule. The lower the responsiveness, the faster the reaction time of the glass ampoule. JOB THERMO BULBS can meet all customer’s RTI requirements by combining different liquids (G or F) with different ampoule diameters. Each JOB THERMO BULB can be identified with regard to its response time by the type designation on the bulbs.

Standard response applications RTI>80

JOB Thermo Bulbs G5 can be used for all applications requiring standard response sensitivities (RTI < 80 ms1/2) as required by regulatory approvals in the USA, Europe, and Asia.

Special applications 50 < RTI < 80

JOB Thermo Bulbs F5 and F4 are used for applications where an average RTI between 50 and 80 is required.

Fast, super-fast and ultra-fast applications RTI<50

JOB Thermo Bulbs F3 and F3-SP are used in applications where products are used for, among other things, Life-Safety applications, such as in residential buildings and in cases where insurers’ hazard classifications require quick response times from sprinklers. The super-fast and ultra-fast glass ampoules F3-F, F2.5, F2 and F1.5 are specifically intended for use in high-performance products where very early triggering is required, e.g. B. ESFR sprinklers or water mist products.


Design flexibility

JOB uses self-drawn glass tubes. This offers enormous flexibility, as glass ampoules with different diameters, aspect ratios and strength/RTI specifications can be produced individually depending on customer requirements.

Trigger temperatures

The different colours of the liquid in the JOB THERMO BULBS represent different trigger temperatures. The colouring of the ampoules complies with all national and international standards for colour/temperature information, e.g. UL 199, FM, TFRI, EN 12259 and ISO 6182-1.


JOB has invented a label to ensure traceability. Each individual JOB THERMO BULB is marked with the type and individual batch number. Each batch can be traced back to the raw material, as well as all test data obtained during the manufacturing and quality processes.


JOB Thermo Bulbs are produced to strict internal quality standards in accordance with the latest version of ISO 9001 to meet all regulatory authority requirements worldwide and to comply with government regulations, where applicable. JOB’s fully automated optical measuring devices carry out more than 1000 measurements in 12 different orientations on the inside and outside of each ampoule.

Product Certificates & Recognitions


For further information, please contact Jürgen Teschner.

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Glass-based Fuse

Thermo Bulb Link


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