The temporary closure of two key sources of carbon dioxide gas, including Orica's controversial explosives plant near Newcastle, is causing supply shortages of the essential ingredient that makes soft drinks bubble.

The major supermarkets say supply disruptions have been minimal so far, but there could be shortages of soft drink if carbon dioxide production does not return to normal soon.

Orica's Kooragang Island explosives plant, which produces ammonia, makes carbon dioxide as a by-product.

The plant has been closed since August following an accident and is only now in the process of slowly being brought back online.

Gas supplier BOC runs a carbon dioxide production facility at Kooragang Island which remains out of action until the explosives plant resumes feeding it raw gas for processing.

BOC says it is sourcing alternative supplies from Queensland and Victoria to maintain supply in New South Wales.

"BOC is currently maintaining normal CO2 supply in other Australian states," the company said in a statement.

Another major source of CO2, Origin and AWE's Lang Lang processing plant in Victoria, is closed for upgrades for about four months.

The production disruptions are starting to hurt supply to Australia's major soft-drink makers.

Schweppes says it has experienced a shortage of CO2 at its largest east coast facilities over the past two months.

"As a consequence of this shortage, we have not been able to produce the volume of soft drinks that we normally would be producing at this time of the year, particularly at our factory in Victoria," the company said in a statement.

"This has resulted in product shortages, largely in Victoria. We have put several workarounds in place to minimise the impact to customers."

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Schweppes's production is also being cut by a lockout of about 150 staff at a factory in Victoria.

A Coles spokesman says the supermarket giant has seen an impact on the availability of some Schweppes products, but has so far still been able to cover that with supplies from other providers.

A Woolworths spokeswoman says the company is watching the situation closely.

"We've not yet experienced notable supply shortages of carbonated products. Having said that, we would be concerned about supply if the CO2 shortage was not rectified very soon," the company said.

Schweppes says its carbon dioxide supplier has advised it will be increasing supplies from the end of next week, allowing full soft drink production to resume.

But Orica says the restart of Kooragang Island is a complex process and there is no firm timeline for the resumption of full production.