The “rancid” smell from a Colorado pet food factory is ruining the lives of people living nearby, who say the gag-inducing odor is so bad they can’t even have their windows open.

Residents within a mile radius of the Nestle-Purina Petcare Co plant in Denver’s Elyria-Swansea neighborhood say the “noxious” smell is “like someone barfed in your back yard and then baked it in the sun”.

They claim that, for two years, they have suffered pounding headaches and watering eyes caused by the nauseating stench, prompting a class action lawsuit against the company that they allege “negligently and knowingly” failed to design, operate and maintain the factory.

Two residents filed a complaint against the company, which owns and operates the pet food factory in an area where more than 2,000 people live. They claim the facility produces an overwhelming “highly odiferous” smell that leaves those living within a mile radius of it struggling.

“[You] can’t plan an outside event… can’t have windows open. You would rather be too hot inside than have the smell come in,” Robert Fields, one of the plaintiffs said in the lawsuit filed on Tuesday.

Mr Fields’ comments are echoed by at least 50 other residents who have joined the lawsuit and described the scent in detail.

“I would describe the smell as rancid,” Robert Boughner and Kelly MacNeil, two putative class members, said to lawyers representing the plaintiffs. “It’s like someone barfed in your back yard and then it baked in the sun and then you put a fan on the smell to keep it circulating.”

The group alleges that Nestle-Purina “negligently and knowingly” failed to design, operate and maintain the factory – thus causing the “rancid” smell.

They are seeking compensatory damages and an injunction on state and federal regulations.

Mr Fields and his co-plaintiff, Loren Oritz, say that members of the community have been complaining about the smell to the Colorado Department of Health and Environment (CDHE) for at least two years.

In one complaint from August 2022, a person said, “Purina is releasing something so toxic that it’s making our eyes water over a mile away…”

A few months later, in January 2023 another complainant said the smell “is so strong it makes you gag… at least once a week.”

When CDHE employees investigated the factory in 2021 they noted the odor “was very strong”. During a follow-up visit, a nasal ranger indicated the smell exceedance the state’s regulation of the 8:1.

Employees noted that plasma units were “overdue for routine maintenance” but because of pandemic restrictions, the Canadian company that would normally tend to them could not reach it.

After alerting Nestle-Purina of the odors, the company agreed to comply with odor emissions through a 2022 proposed plan. But residents continued lodging complaints.

A spokesperson for Purina said they cannot comment on specifics of pending litigation but that, “Purina is a proud member of the Denver community, and we’ve operated our York Street factory since 1930. Throughout this time, we have remained committed to being the best neighbor we can be, and that won’t change.”