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Property, plant and equipment - Summary of elements of property, plant and equipment (Details) - USD ($) $ in Thousands | Sep. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Property, plant and equipment |  |
Subtotal | $ 67,213 | $ 63,998
Less: Accumulated depreciation | (44,432) | (42,444)
Total | 22,781 | 21,554
Land |  |
Property, plant and equipment |  |
Subtotal | 1,255 | 1,255
Land improvements |  |
Property, plant and equipment |  |
Subtotal | $ 319 | 319
Land improvements | Minimum |  |
Property, plant and equipment |  |
Property, plant and equipment, Estimated Lives | 6 years |
Land improvements | Maximum |  |
Property, plant and equipment |  |
Property, plant and equipment, Estimated Lives | 10 years |
Buildings |  |
Property, plant and equipment |  |
Subtotal | $ 1,446 | 1,446
Buildings | Minimum |  |
Property, plant and equipment |  |
Property, plant and equipment, Estimated Lives | 25 years |
Buildings | Maximum |  |
Property, plant and equipment |  |
Property, plant and equipment, Estimated Lives | 39 years |
Building improvements |  |
Property, plant and equipment |  |
Subtotal | $ 3,624 | 3,569
Building improvements | Minimum |  |
Property, plant and equipment |  |
Property, plant and equipment, Estimated Lives | 25 years |
Building improvements | Maximum |  |
Property, plant and equipment |  |
Property, plant and equipment, Estimated Lives | 39 years |
Cylinders |  |
Property, plant and equipment |  |
Subtotal | $ 12,878 | 12,957
Cylinders | Minimum |  |
Property, plant and equipment |  |
Property, plant and equipment, Estimated Lives | 15 years |
Cylinders | Maximum |  |
Property, plant and equipment |  |
Property, plant and equipment, Estimated Lives | 30 years |
Equipment |  |
Property, plant and equipment |  |
Subtotal | $ 33,790 | 32,525
Equipment | Minimum |  |
Property, plant and equipment |  |
Property, plant and equipment, Estimated Lives | 3 years |
Equipment | Maximum |  |
Property, plant and equipment |  |
Property, plant and equipment, Estimated Lives | 10 years |
Equipment under capital lease |  |
Property, plant and equipment |  |
Subtotal | $ 315 | 315
Equipment under capital lease | Minimum |  |
Property, plant and equipment |  |
Property, plant and equipment, Estimated Lives | 5 years |
Equipment under capital lease | Maximum |  |
Property, plant and equipment |  |
Property, plant and equipment, Estimated Lives | 7 years |
Vehicles |  |
Property, plant and equipment |  |
Subtotal | $ 2,213 | 2,081
Vehicles | Minimum |  |
Property, plant and equipment |  |
Property, plant and equipment, Estimated Lives | 3 years |
Vehicles | Maximum |  |
Property, plant and equipment |  |
Property, plant and equipment, Estimated Lives | 5 years |
Lab and computer equipment, software |  |
Property, plant and equipment |  |
Subtotal | $ 3,304 | 3,304
Lab and computer equipment, software | Minimum |  |
Property, plant and equipment |  |
Property, plant and equipment, Estimated Lives | 2 years |
Lab and computer equipment, software | Maximum |  |
Property, plant and equipment |  |
Property, plant and equipment, Estimated Lives | 8 years |
Furniture and fixtures |  |
Property, plant and equipment |  |
Subtotal | $ 1,125 | 1,125
Furniture and fixtures | Minimum |  |
Property, plant and equipment |  |
Property, plant and equipment, Estimated Lives | 5 years |
Furniture and fixtures | Maximum |  |
Property, plant and equipment |  |
Property, plant and equipment, Estimated Lives | 10 years |
Leasehold improvements |  |
Property, plant and equipment |  |
Subtotal | $ 865 | 865
Leasehold improvements | Minimum |  |
Property, plant and equipment |  |
Property, plant and equipment, Estimated Lives | 3 years |
Leasehold improvements | Maximum |  |
Property, plant and equipment |  |
Property, plant and equipment, Estimated Lives | 5 years |
Construction-in-progress |  |
Property, plant and equipment |  |
Subtotal | $ 6,079 | $ 4,237

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