Two summers ago, Chris Correia stepped into her backyard and took a whiff of her new neighbour. She was overcome by the smell of frying oil and spices enveloping her Scarborough property.

"It just took your breath away," she said.

She called Surati Sweet Mart, makers of traditional Indian fried snacks and baked goods, and introduced herself, explaining that her backyard overlooks its Middlefield Road plant.

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"I said, 'I don't mean to be rude, but is that smell coming from your company?' They told me it was exhaust. I said, 'Thank you' and I hung up, and started crying."

A dispute between the family-owned Surati and residents of the Middlefield neighbourhood, in the McCowan Road and Finch Avenue area, is just the latest urban odour clash, and highlights the tension that can arise when industry and homes sit close together. There have been similar battles involving a Lush soap factory in Etobicoke, a Balzac's Coffee location in Stoney Creek, and the Nitta Gelatin plant, where pigskins are turned into gelatin in the Junction Triangle neighbourhood of Toronto.

Surati says it has done all it can to appease residents, including installing an odour-abatement system and cutting back shifts.

The company bought the 65,000-square-foot plant to boost production to three shifts because it says it can't keep up with demand for its chips, crackers and cookies. But soon after Surati moved in, during the summer of 2015, the complaints started piling up.

Residents banded together, pushing politicians for action, organizing a public meeting and demanding that the company do something about the smell they say has them hunkering down in their homes.

The two sides are at a stalemate.

The company has complied with requirements from the Ministry of the Environment and Climate Change, hiring a consultant and installing a system in November to inject ozone to neutralize exhaust from fryer units. In all, the company says it has spent $506,000 and its consultant has found a 74-per-cent reduction in peak odours.

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"As a measure of good faith, we have shut down the midnight shift on the frying lines and we reduced the weekend shift," said Shalini Sheth, director of operations. "That means no overtime for our employees."

When they do need to run extra shifts, the company sends e-mails to neighbours. The extra shifts are happening more often, say the residents, and some days the smell is worse than ever.

"Odour is subjective and can't be eliminated completely. We have done our part and we're continuing to work with the ministry," said Ms. Sheth, adding the company had no complaints in 35 years at its previous Toronto location – also in a residential area – near Victoria Park Avenue and Lawrence Avenue East. "To make sure you are fixing the right thing takes time. I understand that causes some frustration."

But neighbours say they've lost two summers and still can't enjoy their properties. On humid and still days, they describe being able to practically taste the heavy smell of cooking oil. They drive their dogs to other neighbourhoods for walks and backyard pools sit empty on the hottest days because their children don't want to go outside. Even avid gardeners have retreated indoors.

It takes just minutes for hair and clothes to carry the smell when residents venture outside.

"It's kind of like putting your head into a fryer," said CY Au-Yeung, who grew up in the neighbourhood.

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Liz Gosse-Davidson, who has lived in her home more than 30 years, blames the odour for increased asthma symptoms, saying she's used almost a whole inhaler in a year when they normally last five.

The residents mostly place the blame on city regulations that allow a company such as Surati so close to homes. The plant is zoned for light industrial use, which includes food manufacturing. The neighbours contend industrial-scale grease frying is not light industrial.

"The city needs to do something about the zoning," Mr. Au-Yeung said. "It doesn't make sense to put a plant like that so close to a residential area, directly bordering our backyards. Anyone who thinks straight wouldn't do that."

The City of Toronto is required by the province to ensure it has sufficient employment lands, spokeswoman Tammy Robinson said. "Employment lands within the city are a finite land resource, and are the only places across the city that can accommodate certain manufacturers, including those that emit odours. In order to maintain a diverse economy, these type of businesses need to be able to thrive in the city."

The neighbours say City Councillor Chin Lee has not responded to them in more than a year. In the past, he's told them the company has a right to operate and residents say his staff has even warned them their public comments could get them sued by Surati.

Mr. Lee did not respond to several requests for comment.

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The neighbours stress they have nothing against the company or its products, but they don't believe its operations should be allowed to affect their lives.

"I know they have a right to be here, but I have a right to have my children play outside or to have our windows open," Ms. Correia said. "What about our rights? We pay property taxes. We didn't sign up for this."

The family behind Surati is not unsympathetic.

"We feel for them, too," Haren Sheth, the company's chief executive officer, says of the neighbours. "They weren't having issues before, but we are trying to keep pace with our competitors, too. Odour and noise are tricky. We need to co-exist."

The company is in the hands of the second and third generations of the family and may soon have its fourth generation hands on deck, too.

All of its products are chickpea- or flour-based and vegetarian. The plant also has a retail operation selling its packaged products and fresh-made food.

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Surati has four distribution centres in the United States and a plant in India that sources raw ingredients. Sixty per cent of its global sales of $20-million are exports to the United States, Australia and New Zealand. Surati products are sold in Canada in Loblaws, Sobeys, Food Basics, Costco, and independent Indian groceries.

Shalini Sheth points to consultant reports and Ministry of the Environment weather modelling information that show so-called peak odours are being reached in 50 measuring locations in the neighbourhood just 0.2 per cent of the time.

"The neighbours will say the smell is unbearable, but we aren't experiencing the same. There is an odour, but it's not the extreme being described."

The Ministry of the Environment is reviewing source testing conducted in February, spokesman Gary Wheeler said. "The company must demonstrate to the ministry that it has taken all reasonable measures to address the odour. The ministry's role is to ensure that companies take measures to ensure their operations do not impact residences in the area."

Ms. Sheth says her company has done everything it can to be responsive to neighbours, including spending $300,000 on an indoor freezer in response to complaints about noise from compressors.

But when there is conflict between industrial and residential users, "the onus can't always be put on the business. We have to co-exist." Surati supports city infrastructure and employs 125 people, she says, often providing a first job to newcomers.

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Odour expert Ray Porter, who has not done any work with Surati but has worked with waste-water treatment, landfill, food and industrial clients for 35 years, says "odour acceptance" in a community is based on four factors: frequency, intensity, duration and offensiveness.

"Even pleasant odours all the time are too much. Cooking or baking odours can be offensive if it's every day," said Mr. Porter, who is a knowledge leader with Montreal's Odotech, and is based in Boston.

Mr. Porter says an odour is a nuisance if it regularly prevents people from enjoying their home. Odours that come frequently and last a long time can cause stress, anxiety and physical reactions.

"Food odours are recognizable and distinctive. Once it's recognizable, there is anticipation of it and residents can recognize it at very low levels," he said. "There is a plant that roasts peanuts for peanut butter near my house. I drive by and I think, 'Oh, peanut butter. I want a sandwich.' But if I lived closer and the smell was there all the time, that's the last thing I'd think."