How you refill an oxygen tank depends on which type of system you have. Most home oxygen users refill portable tanks using either a concentrator-based transfilling device or a stationary liquid oxygen reservoir. Some tanks need to be returned to your oxygen supply company for professional refilling. Here’s how each method works and what to keep in mind for safety.
Three Ways Oxygen Tanks Get Refilled
Home oxygen setups generally fall into three categories, and each one has a different refill process:
- Concentrator with a transfilling unit: A device like the Invacare HomeFill sits on top of your oxygen concentrator and compresses room air into a portable cylinder. This is the most common home refill method for compressed gas tanks.
- Liquid oxygen reservoir: A large stationary tank in your home stores liquid oxygen. You fill a smaller portable unit by connecting it to the top of the reservoir. The liquid converts to gas as you use it.
- Supplier exchange or refill: Your durable medical equipment (DME) provider delivers full tanks and picks up empty ones on a regular schedule. Some tanks can only be refilled this way.
Filling a Tank With a HomeFill Transfiller
Transfilling systems like the Invacare HomeFill are designed for smaller portable cylinders, typically M4, M6, and similar sizes. Filling larger E-size tanks is possible with the right adapter, but your DME supplier needs to provide tanks equipped with the correct nozzle for your specific system.
The basic process:
- Turn on the oxygen concentrator (the bottom unit). It must be set to 3 liters per minute or lower to fill a tank.
- On the transfiller (the top unit), make sure the silver sleeve is down and the green dots are visible.
- Place the portable tank in the cradle. Match the gold connector on the tank to the gold connector on the transfiller, then press down until it clicks into place.
- Turn on the transfiller. An orange light will appear for about five minutes while the unit warms up. It then switches to filling automatically.
- When the tank is full, a green light comes on. Fill times vary depending on tank size.
- Turn off the transfiller, then hold down the silver ring and lift the tank out of the cradle.
One thing to note: transfilling from a concentrator is slower than other methods because the device is pulling oxygen from room air, concentrating it, and compressing it into the cylinder. Plan ahead rather than waiting until your portable tank is completely empty.
Filling a Portable Liquid Oxygen Unit
If you have a liquid oxygen system, your portable unit connects directly to the top of the stationary reservoir. The fill is fast, typically one and a half to two minutes, but requires careful technique because the equipment operates at extremely cold temperatures.
Start by inspecting the transfer connections on both the portable and the reservoir. They need to be clean, dry, and free of lint. If the connections are wet, the units can freeze together during the fill. Turn the flow rate on the portable unit to the “off” position before connecting.
Align the portable unit’s fill connector to the recessed area on top of the main reservoir, place one hand on top of the portable, and press straight down to start filling. While holding downward pressure, flip the vent valve lever straight out to open it. About 15 to 20 seconds into the fill, close and reopen the vent valve to break up any ice crystals that may have formed.
You’ll hear a hissing sound during filling and may see a small vapor cloud. Both are normal. Keep holding the unit down and don’t walk away. When the hissing changes to a spitting noise, the tank is full. Close the vent valve, then disconnect by holding the carrying strap and pressing the release button.
If the units freeze together, don’t force them apart. Let them sit for 10 to 30 minutes to thaw naturally, then try separating them again. If they still won’t release, call your equipment supplier.
Safety Precautions During Refilling
Oxygen itself doesn’t burn, but it makes everything around it burn faster and more intensely. Even a small oxygen leak in a poorly ventilated room can create a dangerous environment. Fill your tanks in a well-ventilated area, away from any heat source, open flame, or pilot light. Industrial safety standards recommend ventilation openings with a flow area greater than 1/100 of the room’s floor area, placed on opposite sides of the space. In practical terms, a room with a window open on each side works well. If natural airflow isn’t possible, use a fan.
Never use oil, grease, petroleum jelly, or hand lotion on or near oxygen valves, regulators, or connections. Hydrocarbons can ignite spontaneously when exposed to high-concentration oxygen. Gauges and regulators designed for oxygen use are specifically labeled “Use No Oil” for this reason. Before handling your equipment, wash your hands and make sure they’re free of any oily residue.
When you’re done filling, close the main supply valve on your stationary unit to prevent slow leaks while the equipment sits idle.
Equipment Checks Before Each Refill
Before connecting a portable tank for filling, give it a quick visual inspection. Look for obvious damage, corrosion, or cracks around the valve and body. Check that O-rings and seals aren’t cracked or missing. Regulators and valves should also be inspected regularly for corrosion or deterioration.
Oxygen cylinders require a formal visual inspection once a year and hydrostatic pressure testing every five years, both performed by an authorized inspector. Your gas supplier or DME company typically handles this. The hydrostatic test date is stamped on the cylinder itself. If your tank is past due, don’t refill it. Contact your supplier for a replacement or to schedule testing.
Prescription Requirements
Medical oxygen is classified as a drug by the FDA, which means you need a valid prescription to obtain it and get refills. Your prescribing doctor specifies your flow rate and how many hours per day you need supplemental oxygen, and your supplier keeps this prescription on file.
There is one narrow exception: oxygen intended purely for emergency resuscitation use can be provided without a prescription, but only when it’s administered by properly trained personnel using equipment that delivers at least 6 liters per minute for a minimum of 15 minutes. This exception exists for first responders and rescue organizations, not for routine home use.
What Medicare Covers
Medicare Part B covers the rental of home oxygen equipment, including the supplies and services needed to keep it running. To qualify, your doctor must document that you aren’t getting enough oxygen and that your blood oxygen levels fall within a specific clinical range.
You rent the equipment from a supplier for 36 months. During that period and for an additional 24 months after (up to five years total), the supplier is required to maintain the equipment and provide related supplies at no extra charge beyond your standard cost sharing. After you meet the Part B deductible, you pay 20% of the Medicare-approved amount.
If you use a concentrator with a transfilling system, you may owe a coinsurance payment for maintenance and servicing every six months, but only if the supplier actually comes to your home to inspect the equipment. They can’t bill you for a visit that didn’t happen. If you use tanks that require delivered gas or liquid oxygen contents, Medicare continues to pay for those deliveries even after the 36-month rental period ends. You’ll still owe 20% of the approved amount for each delivery.