This is an action to recover damages for property damage caused by a fire which originated on or near a railroad right of way and spread onto plaintiffs’ land. The action was commenced nearly four years after the damage occurred. The defendants demurred to the complaint on the ground that it disclosed on its face that the action was barred by the two-year statute of limitations, ORS 12.110 (1). ① The trial court sustained the demurrer and entered judgment for defendants. Plaintiffs appeal.

Plaintiffs’ eomplaint alleges that the defendants *565 negligently caused the fire to occur and negligently permitted it to escape and spread onto plaintiffs’ range land. Plaintiffs contend that the damage was the result of a trespass caused by defendants’ negligent conduct and that the applicable statute of limitation is ORS 12.080 (8) providing for a six-year limitation period. ②

Defendants contend that the action is “based upon negligence or trespass in the case” and therefore is barred by the two-year statute of limitation (ORS 12.110 (1)). The trial court agreed with defendants’ analysis and sustained their demurrer.

A trespass arises when there is an intrusion upon the land of another which invades the possessor’s interest in the exclusive possession of his land. The intrusion may be caused by either intentional, negligent, reckless or ultrahazardous conduct. ③ Whether the invasion of the plaintiff’s interest is direct or indirect is immaterial in determining whether the invasion is trespassory. ④

The spread of the fire from defendants’ land onto plaintiffs’ land was an intrusion of a character sufficient to constitute a trespass. In Martin v. Rey *566 nolds Metals Company, 221 Or 86, 342 P2d 790 (1960), cert. den., 362 US 918, we held that a trespassory intrusion resulted when the defendant caused certain fluoride compounds in the form of gases and particulates to become airborne and settle upon plaintiff’s land, recognizing that a trespass can result from an intrusion by invisible as well as visible forces and that it is the force of the instrumentality rather than its size which is significant in determining whether a trespass has been committed. We reaffirmed this position in Davis v. Georgia-Pacific, 251 Or 239, 242, 445 P2d 481 (1968), when we said, “[t]he traditional concept that a trespass must be a direct intrusion by a tangible or visible object as set forth in Norwood v. Eastern Oregon Land Co., 139 Or 25, 37, 5 P2d 1057, 7 P2d 996 (1932) has been abandoned in this state.”

A. fire, although once regarded as a “tenuous material substance, and anciently classified with air, earth and water as one of the four elements” (Webster’s Dictionary) is now deemed only a process — the process of combustion capable of operating to cause harm to a person’s interest in the exclusive possession of land, just as the chemical process in Martin v. Reynolds Metals Company was capable of causing a similar invasion.

We hold that the invasion in the present case resulting from defendants’ negligent conduct constituted a trespass. ⑤ Therefore, the action is governed by ORS 12.080 (3).

The issue presented in this appeal again serves to remind us of the need for legislative revision of the *567 statutes on the limitation of actions. ⑥ There would appear to he no reason for providing different limitation periods in actions for invasions of interests in land, whether the action is in trespass or nuisance and whether the conduct causing the invasion is intentional, negligent, reckless or ultrahazardous. ⑦

Reversed and remanded.