CO₂ Cylinder Requalification: Water Jacket vs Proof Pressure vs Ultrasonic Testing
If you own or manage CO₂ fire extinguishers or compressed gas cylinders, you’re responsible for ensuring they’re tested and certified for safe use. In Canada, this requalification process is required every few years and must follow standards set by Transport Canada and the CSA (Canadian Standards Association).
But not all testing methods are the same. Depending on the cylinder type, age, and markings, you may have options—or specific requirements—for how that requalification is done.
The three most common methods for CO₂ cylinder requalification are:
Water Jacket Testing
Proof Pressure Testing
Ultrasonic Examination (UE)
Let’s break down what each method involves, and when it’s used.
1. Water Jacket Testing (Volumetric Expansion Test)
This is the most common and widely accepted hydro testing method in Canada.
How it works:
The cylinder is placed inside a sealed water-filled chamber (jacket).
The cylinder is filled with water and pressurized beyond its normal limit.
As the cylinder expands under pressure, the displaced water is measured.
The amount of permanent expansion vs temporary expansion is analyzed.
Too much permanent expansion indicates a structural failure, and the cylinder must be removed from service.
Where it's required:
Water jacket testing is required for most CO₂ cylinders, especially steel cylinders under CSA B339. It is the gold standard for detecting internal wall thinning, cracks, and fatigue.
2. Proof Pressure Testing
This is a simplified hydrostatic test method used mainly for non-liquefied gas cylinders, but may also be permitted for certain low-pressure or smaller CO₂ cylinders depending on manufacturer specs.
How it works:
The cylinder is filled with water and pressurized.
No expansion measurement is taken.
Instead, the cylinder is simply checked for leaks or visible deformation.
Pros:
Faster and less complex than water jacket testing
Lower cost
Can be done with simpler equipment
Cons:
Does not detect permanent deformation or wall thinning
Not accepted for all cylinder types
In most commercial applications in Ontario, this method is not the default for CO₂ extinguishers unless specifically approved.
3. Ultrasonic Examination (UE)
This is a non-invasive, non-hydrostatic test method used mostly for aluminum cylinders and specific high-performance tanks, such as those used in SCBA gear.
How it works:
A handheld ultrasonic device is used to scan the cylinder’s wall thickness.
The technician checks for cracks, pitting, corrosion, or thinning without needing to open or pressurize the tank.
Where it’s used:
SCBA cylinders
Some aluminum CO₂ cylinders, if certified for UE
Cylinders with DOT-SP or TC-SU permits
Ultrasonic testing must be performed by a facility certified for UE testing. It’s often used as an alternative to hydro testing for cylinders that would otherwise need to be removed from service due to age.
Learn more from CSA B339 Cylinder Requirements
Which Method Is Required for Your Cylinder?
It depends on:
Cylinder material (steel vs aluminum)
Cylinder markings and specifications (TC, DOT, SP, SU, etc.)
Age and previous test history
Regulatory requirements for your industry
Most commercial-grade CO₂ fire extinguishers in Ottawa require water jacket testing every 5 years. In some cases, SCBA cylinders may qualify for ultrasonic testing instead.
If you’re unsure, check your cylinder’s markings or speak with a Transport Canada-authorized testing facility.
CO₂ Cylinder Hydro Testing in Ottawa
At Rapid CO₂, based in Ottawa, Ontario, we provide certified hydro testing for CO2 cylinders for home and businesses as well as CO2 fire extinguishers. We do not perform proof-pressure or ultrasonic testing.
Our facility uses Transport Canada-approved methods and keeps your equipment labeled, certified, and fully compliant. We can also help you determine the correct requalification method for each cylinder in your inventory.
To schedule a hydro test, call 613.299.8412.
