Ripening fruit (any fruit, even when picked from the plant) secretes ethylene gas as part of their natural process.
Ethylene (among other gases) is responsible for triggering the ripening of fruits, and the senescence of pollinated flowers.

Ethylene is actually produced inside the plant, and delivered to the flowers and fruits. Ripening fruit receives heavier doses of ethylene and therefore provides a larger chance of expending the ethylene in the form of ethylene gas.
The ethylene in the plant rarely escapes through the plant membranes. But do be careful about pruning plants inside the greenhouse (or chopping them up in preparation for composting).

Obviously you do not want ripening fruit in close proximity of flower that you do not want to wilt as it would trigger the flowers to senesce without being pollinated first.

Kerosene heaters also produce trace amounts of ethylene gas as a byproduct, and is actually used by fruit warehouse companies to induce faster ripening of fruit stock that were picked green during harvest.

Info Link 1
Info Link 2
Ethylene and Auxin Participation in Pollen Induced Fading of Vanda Orchid Blossoms

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