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Sulfur dioxide

Sulfur dioxide suppliers and sourcing guide

Sulfur dioxide is a colorless gas with a sharp odor, made by burning sulfur or as a byproduct of metal ore roasting, then purified and liquefied under pressure. In food it is used mainly in winemaking and for dried fruit to control microbes and browning. Wineries and processors buy it as liquefied gas in cylinders or as prepared aqueous solutions, while many smaller producers dose it in the form of potassium or sodium metabisulfite instead.

See suppliersWhat to ask for on the COA
Also known as
Sulphur dioxide · SO2 · E220 · CAS 7446-09-5
Facts checked
November 2026

Forms and grades of sulfur dioxide

Suppliers sell different products under the same name. Specify the one you need.

  • Liquefied gas

    Pure sulfur dioxide in pressurized cylinders or tonners, dosed through a gas manifold or dissolved in water on site.

  • Aqueous solutions

    Sulfur dioxide dissolved in water at a stated strength, used to dose wine and juice by volume.

  • Sulfur wicks and discs

    Elemental sulfur that releases sulfur dioxide when burned, used to treat empty barrels.

  • Metabisulfite salts

    Potassium and sodium metabisulfite, solids that release sulfur dioxide in acidic solution and are separate ingredients.

What to check on the COA

Compare each result with your own specification when the lot arrives.

Purity
Sulfur dioxide content of liquefied gas, usually 99.9 percent or more.
Moisture
Water in the liquefied gas, which makes it corrosive to equipment.
Non-volatile residue
Residue left after the gas evaporates.
Solution strength
For aqueous solutions, sulfur dioxide concentration by iodometric titration, which sets the dose.
Heavy metals
Lead, arsenic and other metals by ICP-MS or ICP-OES against the supplier's specification or the Food Chemicals Codex (FCC) limits.

Storage, lots and expiry

Storage and shelf life

Store sulfur dioxide cylinders upright, secured, in a cool, well-ventilated area away from heat, following the gas supplier's handling and safety data sheet; the gas is toxic. Aqueous solutions lose strength over time, especially when opened, so keep them tightly closed and cool. Shelf life follows the supplier's specification, and solutions are re-titrated before use.

Lots and expiry dates

Record the cylinder or solution lot and, for solutions, the measured strength at the time of use, since sulfur dioxide escapes after opening. Log additions per batch so total sulfite in the finished product can be tracked for labeling.

Regulatory status

Facts from regulators and standards bodies, each linked to its source.

  • 21 CFR 182.3862 lists sulfur dioxide as GRAS when used in accordance with good manufacturing practice, except that it is not used in meats, in foods recognized as a source of vitamin B1, or on fruits or vegetables served or sold raw or presented as fresh.

    Source: ecfr.gov (opens in a new tab)

  • Under 21 CFR 101.100(a)(4), a sulfiting agent such as sulfur dioxide is detectable, and so cannot be treated as an insignificant incidental additive, at 10 ppm or more in the finished food.

    Source: ecfr.gov (opens in a new tab)

  • 7 CFR 205.605(b) allows sulfur dioxide only in wine labeled "made with organic grapes," with total sulfite not exceeding 100 ppm.

    Source: ecfr.gov (opens in a new tab)

This is general information, not regulatory advice. Status differs by country and by how the ingredient is used, so check the rules for your product and market.

Sulfur dioxide suppliers

Manufacturers and distributors whose own websites say they sell it.

We are checking sulfur dioxide suppliers now

Every listing is checked against the supplier’s own website before it goes live, so this list fills in over the coming weeks. The specs and COA checklist above are ready today.

Sell sulfur dioxide? Request a listing

Frequently asked questions

What forms of sulfur dioxide can brands buy?

Common forms include liquefied gas, aqueous solutions, sulfur wicks and discs and metabisulfite salts. Ask each supplier for the specification sheet of the exact grade they quote.

What should the COA for sulfur dioxide include?

Expect purity, moisture, non-volatile residue, solution strength and heavy metals, each with its method, specification and result for that lot.

How should sulfur dioxide be stored?

Store sulfur dioxide cylinders upright, secured, in a cool, well-ventilated area away from heat, following the gas supplier's handling and safety data sheet; the gas is toxic. Aqueous solutions lose strength over time, especially when opened, so keep them tightly closed and cool. Shelf life follows the supplier's specification, and solutions are re-titrated before use.

What is the regulatory status of sulfur dioxide?

21 CFR 182.3862 lists sulfur dioxide as GRAS when used in accordance with good manufacturing practice, except that it is not used in meats, in foods recognized as a source of vitamin B1, or on fruits or vegetables served or sold raw or presented as fresh. Under 21 CFR 101.100(a)(4), a sulfiting agent such as sulfur dioxide is detectable, and so cannot be treated as an insignificant incidental additive, at 10 ppm or more in the finished food. 7 CFR 205.605(b) allows sulfur dioxide only in wine labeled "made with organic grapes," with total sulfite not exceeding 100 ppm.

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