Ripening Ethylene & Safe Dose for Even Ripening

Ethylene is the natural plant hormone that triggers ripening. A small, controlled dose in a sealed chamber signals mature-green fruit such as banana, mango and tomato to ripen evenly and on schedule. Done right it gives uniform colour, texture and flavour — far better and far safer than the banned, hazardous practice of using calcium carbide.

Ethylene per dose (mL) = chamber volume (L) × target ppm ÷ 1,000,000, because ppm is parts per million by volume. For example a 20,000 L chamber at 100 ppm needs 20,000 × 100 ÷ 1,000,000 = 2 mL of pure ethylene. You re-dose each time the chamber air is exchanged to keep the concentration at target.

Around 100 ppm suits banana and mango and most climacteric fruit; some operations use 10–150 ppm depending on fruit, ripeness and chamber tightness. Above roughly 100–150 ppm there is little extra ripening benefit, so there is no point going higher. The calculator lets you set the target ppm for your fruit and practice.

Fruit and the ripening process produce carbon dioxide that must be vented, and chambers are never perfectly sealed, so the air is exchanged periodically. Each air change carries away the ethylene, dropping the concentration below target. Re-dosing per air change tops it back up, which is why the tool multiplies the per-dose amount by the number of doses.

Hold the chamber at about 18–22 °C with high relative humidity (around 90–95%). Warmer than that can give soft, blotchy fruit; colder slows or stalls ripening. High humidity stops the fruit drying and shrivelling. After the ethylene treatment period, ventilate the chamber to clear gas and let ripening complete.

Yes — calcium carbide is banned in many countries because it releases acetylene contaminated with arsenic and phosphorus and poses a fire risk, and it gives poor, uneven ripening. Controlled ethylene gas from a food-grade source ripens fruit uniformly and safely, with no toxic residue, which is why it is the recommended method.

From a food-grade ethylene cylinder metered into the chamber, or from ready-made ethylene-releasing ripener sachets or generators sized for a chamber. Use only food-grade ethylene intended for ripening, and follow the supplier's metering or sachet instructions alongside the dose this calculator gives.

Pure ethylene is flammable, but the ripening concentration of around 100 ppm is far below the lower flammable limit (about 27,000 ppm), so a correctly dosed chamber is safe. Keep well below the flammable limit, avoid leaks of concentrated gas near ignition sources, and use proper metering — never overdose massively in a sealed room.

Climacteric fruit that continue to ripen after harvest — banana, mango, tomato, papaya, avocado, sapota, kiwi and others — respond well. Non-climacteric fruit such as citrus, grapes and pineapple do not ripen further after picking, so ethylene only degreens citrus rind rather than truly ripening it. The tool is for the climacteric, mature-green types.

The dose maths is exact for the volume and ppm you enter, but real ethylene need depends on how tight the chamber is, how often the air changes, the fruit load and its ripeness. Treat the result as a well-grounded starting dose, monitor the fruit, and adjust the ppm and re-dosing to your own chamber and produce.