Hajukaasua

Hajukaasua is a Finnish term referring to the odor associated with gas leaks, produced by odorants added to natural gas or biogas to make leaks detectable. The odorants are volatile sulfur compounds, typically mercaptans, added during gas processing or distribution to create a distinctive smell independent of the gas itself.

Common odorants include tert-butyl mercaptan and ethyl mercaptan. These substances produce a sulfurous, rotten-egg-like odor that is intended to be noticeable at low concentrations, enabling people to detect leaks before they reach dangerous levels. The practice of odorizing gas is regulated by national and regional standards to ensure consistency and safety across utilities and users.

Detection of hajukaasua relies on the mixture of odorant and gas concentration, but several factors can affect perception. Odor intensity may fade due to ventilation, high gas flow, or degradation of the odorant. Some individuals have reduced or no sense of smell (anosmia or hyposmia), and olfactory fatigue can occur with continuous exposure. In rare cases, equipment or environmental conditions can mask the odor while gas is still present.

Safety guidance associated with hajukaasua emphasizes immediate action. If the smell is detected, do not operate electrical switches or create sparks, extinguish flames if safe to do so, leave the premises, and call the local gas emergency number or utility provider. Do not re-enter until authorities declare it safe. Additional measures include ventilating the area from outside after evacuating and ensuring others are alerted.

Hajukaasua is a practical concept in public safety communications, reflecting the everyday odor cue that signals potential gas leaks.