How do I know that my CO2 pressure gas cylinder still has gas in it?
The cylinder pressure of 50 – 60 bar, depending on the room temperature, remains constant until the cylinder is almost completely empty.
You can read the tare weight on label of the u500 CO2 cylinder. According to this a full u500 CO2 cylinder weighs 1140 g tare + 500 g filling.
What is the reach of a 500g CO2 cylinder?
There is no general answer to this question, as we do not know what the desired number of bubbles for your aquarium is. One bubble contains approx. 0.125 mg CO₂, which corresponds to 4 million bubbles for a 500 g cylinder. At a consumption of 10 bubbles per minute (600 bubbles per hour), this corresponds to 6667 hours, which in turn corresponds to around 277 days or slightly longer than 9 months of an unchanged CO₂ supply.
Please note that this is a rough estimate and does not represent a guarantee about how many days you can actually get out of one compressed gas cylinder.
How can I dispose of my disposable CO2 cylinder?
You can dispose of the empty cylinder as household waste or by taking it to scrap-metal recycling. It is important that the cylinder is completely empty.
Towards the end of the filling process the cylinder pressure rapidly and significantly drops. Does this mean my system is broken?
The rapid drop in the cylinder pressure shortly before the end of the charge does not constitute grounds for complaint, and instead, is normal and unavoidable from a technical standpoint.
Reason: The cylinder is filled approximately halfway with liquid carbon dioxide. You remove gaseous CO₂ from the cylinder; the corresponding share of the liquid CO₂ passes to the gaseous phase; the pressure remains constant. It isn’t until less CO₂ passes from the liquid phase to the gaseous phase that the cylinder pressure begins to drop.
This means your system is functioning normally.
Is there anything I need to know when dealing with CO2 pressurised gas cylinders?
You must observe two points:
1) Cylinder: Reusable cylinders are TÜV tested and this is stamped on the cylinder. This test must be renewed every 10 years, with the bottom of the cylinder and the valve sealing and threaded joint being tested.
2) The carbon dioxide:
Depending on its concentration, carbon dioxide is harmful in the air. From: http://www-organik.chemie.uni-wuerzburg.de/misc/betr_ein/uw-g15.html : The respiratory rate and pulse rate increase at a carbon dioxide concentration of 3-5%. Other symptoms are headaches, discomfort and ringing in the ears. Carbon dioxide concentrations of 8-10% and more cause these symptoms to become more pronounced. This may lead to cramps, fainting, apnoea and death from suffocation.
One 500 g cylinder contains 500 g CO₂. This is equal to 11.36 mol (chemical substance amount unit). One mol of a gaseous substance has a volume of 22.414 l under normal conditions (273.15 K, 101325 Pa), so that 500 g of CO₂ result in a volume of 254.7 l. CO₂ is heavier than air, so that it collects on the ground. This corresponds to a CO₂ height level in the range of 12.735 mm = 1.27 cm for a room of 20 m². If it is mixed completely with the air in a room of 20 m² and a height of 2.5 m (corresponds to 50,000 l), this corresponds to a maximum gas concentration of 0.5 volume %, which is well below the dangerous level.