Immediate Actions Upon Discovering Contamination
If you suspect your portable scuba tank is contaminated, the absolute first step is to immediately remove it from service. Do not attempt to use it or even test the valve. Contamination can range from saltwater and particulates to more dangerous hydrocarbons or carbon monoxide (CO). The risk is not just to the tank’s integrity but, more critically, to the diver’s life. Inhaling contaminated air can cause anything from respiratory irritation to loss of consciousness underwater, which is invariably fatal. Secure the tank in a well-ventilated area, clearly mark it as “CONTAMINATED – DO NOT USE” with a permanent marker or a dedicated tag, and segregate it from clean, in-service equipment to prevent any accidental use.
Identifying the Type and Source of Contamination
Effective handling depends on accurately identifying the contaminant. Contamination isn’t always visible, so you must rely on other clues. Here’s a breakdown of common contaminants and their indicators:
| Contaminant Type | Common Sources | Key Indicators | Primary Health Risk |
|---|---|---|---|
| Hydrocarbons (Oil, Fuel) | Faulty compressor seals, improper lubricants, contaminated intake air. | Distinct petroleum or oily smell; visible sheen or film inside the tank; “diesel” taste in air. | Hydrocarbon poisoning, lung irritation, central nervous system effects. |
| Carbon Monoxide (CO) | Compressor engine exhaust drawn into intake, compressor overheating. | Often odorless and tasteless; symptoms in diver include headache, nausea, dizziness, cherry-red lips. | Carbon monoxide poisoning, leading to hypoxia and death. |
| Particulates (Dust, Rust, Water) | Failed filtration, corroded tank interior (if not properly maintained), moisture intrusion. | Hissing sound from regulator; gritty taste; water spray from the valve; visible rust particles. | Damage to regulator, lung irritation, potential for air embolism if valve freeflows. |
| Excess Moisture | Inadequate air drying at the fill station, condensation inside the tank. | Water droplets from the valve; moisture detected during visual inspection; internal corrosion. | Accelerated internal corrosion of the tank, compromising its structural integrity over time. |
If the contamination is suspected to be CO or hydrocarbons, the tank must be treated as containing hazardous material. For particulates and moisture, the risks are more mechanical and long-term, but the handling procedure remains stringent.
The Professional Decontamination and Requalification Process
This is not a do-it-yourself task. The procedure must be performed by a qualified professional, typically at an accredited scuba repair facility or by a Visual Inspection Technician (VIP) and hydrostatic testing station. The process is meticulous and follows a strict sequence to ensure safety.
Step 1: Safe Depressurization and Disassembly
The technician will first slowly release all remaining air from the tank in a controlled, ventilated environment, often through a filtration system to capture any contaminants. The valve is then carefully removed. This step is critical because forcing contaminated air through a regulator can ruin it.
Step 2: Internal Visual Inspection
Using a specialized borescope or light wand, the technician performs a thorough internal inspection. They are looking for signs of corrosion, pitting, lining failure (in aluminum tanks), and visible contaminants. This inspection alone can determine if the tank is salvageable. Severe internal corrosion often condemns a tank immediately.
Step 3: Cleaning and Purging
If the tank is deemed serviceable, the cleaning begins. The method depends on the contaminant:
- For particulates and moisture: The tank may be rinsed with deionized water and scrubbed with a non-abrasive tool attached to a long rod. It is then dried thoroughly using filtered, oil-free air and heat.
- For oil and hydrocarbons: This requires a more aggressive solvent wash. Technicians use specialized, tank-safe solvents that effectively dissolve oils without damaging the tank’s interior. After multiple solvent rinses, the tank is purged with clean, dry air to evaporate all solvent residues. This cycle may be repeated several times.
- For CO contamination: The tank is repeatedly purged with clean, breathable air to dilute and remove the CO. The air used for purging must be verified as pure to a standard like CGA Grade E.
Step 4: Re-inspection and Hydrostatic Testing
After cleaning, a second internal visual inspection is mandatory to confirm all contaminants have been removed. The tank must then undergo a hydrostatic test to verify its structural integrity. This test involves pressurizing the tank with water to 5/3 of its working pressure to measure permanent expansion. Only after passing this test can the tank be considered safe.
Step 5: Reassembly and Final Air Fill
A cleaned and tested valve is installed with a new O-ring. The tank is filled with air that meets the ANSI/CGA G-7.1 Grade E standard for breathing air, which has strict limits on moisture (dew point of -65°F/-53°C), hydrocarbons (≤5 mg/m³), CO (≤10 ppm), and CO2 (≤1000 ppm).
Cost and Time Considerations
Decontaminating a tank is a significant investment. A simple visual inspection and cleaning for moisture might cost around $50-$75. However, a full decontamination process involving solvent washes, hydrostatic testing, and a new valve can easily exceed $150-$300. The time frame can range from a few days to several weeks, depending on the shop’s workload and the extent of contamination. Weighing this cost against the value of the tank is important; for an older or low-cost tank, condemnation and replacement may be the more economical choice.
Prevention: The Best Strategy
The most effective way to handle contamination is to prevent it from ever happening. This responsibility falls on both the diver and the air filler.
- For Divers: Always use reputable dive shops with certified compressors and filtration systems. Never leave your tank completely empty for extended periods; a small positive pressure (100-200 psi) prevents ambient moisture and contaminants from entering. Store tanks upright in a cool, dry place.
- For Fill Stations: Maintain a strict compressor maintenance schedule, including regular oil changes and filter replacements. Air quality should be tested periodically using laboratory analysis or on-site gas analyzers. Intakes must be located away from potential sources of contamination like vehicle exhaust or industrial fumes.
Implementing these preventative measures drastically reduces the risk, ensuring that every breath you take underwater is as safe as the equipment you trust. The integrity of your air supply is the foundation of safe diving, and there is no room for compromise.