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I don't see where it claims that.

They point out that piped air is one option (which is basically continuous open circuit in these settings; exhausting to outside.). The alternative is oxygen cylinders mounted on the chamber (or inside the chamber), which (generally) require scrubbers.

Oxygen candles are then mentioned; they are essentially a nearly direct replacement for oxygen cylinders, but with somewhat better storability. It is silent on whether co2 scrubbing is needed, but obviously would in the same settings oxygen cylinders would.

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"A candle is an entirely independent source of oxygen from within the refuge chamber. In this way, it’s isolated from common faults found in the other sources:

Compressed Air: The feed can often be compromised during an emergency due to damage to the circuit or carbon monoxide contamination requiring the chamber to be isolated."

The candle is not isolated from the common fault of carbon monoxide contamination. Both Oxygen candles and oxygen cylinders will generally require scrubbers.

I think you are mixing up carbon monoxide contamination and carbon dioxide build up.

They mean that with oxygen candles you don't risk having your very oxygen reserve introduce carbon monoxide in the air you breathe, as it could happen of you have a contamination at the source of compressed air.

Okay, ignoring carbon monoxide contamination. The site also states: "Oxygen cylinders are used in the event compressed air fails and generally require the support of a scrubbing system to remove carbon dioxide and carbon monoxide from the air."

If Oxygen cylinders generally require a scrubber I think it's safe to assume that a Oxygen candle will also need a scrubber.

They list issues with other systems but don't acknowledge the same problems that exist with their own.