Colin Goulding, 31, destroyed the Real Crisp factory in Crumlin, near Newport, South Wales, when he sneaked away for a smoking break on the factory floor.
He worked on a production line boxing packets of crisps, the Daily Mirror reported.
Goulding broke company policy by bringing cigarettes and a lighter down to a storeroom on the factory floor where he was surrounded by flammable material.
But it landed on a pile of crisp packet wrappers, starting a blaze which engulfed the factory in just 10 minutes.
More than than 100 workmates lost their jobs after the fire, including Goulding's parents who also worked there.
Judge Richards, sentencing him to six years and three months behind bars at Newport Crown Court, said: "This is far and away the most serious arson I have ever dealt with as a judge in these courts. This was a ridiculous thing to do."
Goulding, who has already spent 15 months in custody since he was remanded in September 2012, will have to serve at least half of his sentence in prison.
The court heard the defendant, who has learning difficulties and is said to have the "intellectual level" of an 11- to 13-year-old, started the fire at the factory on September 20, 2012, when he flicked a lit cigarette in a flammable area.
He told the court the factory contained around 10,000 litres of cooking oil in its fryers, as well as 30,000 litres in a tanker outside.
The judge described the factory as "like a tinderbox".
You’ve reached your limit of {{free_limit}} free articles this month.
Subscribe now for unlimited access.
Already subscribed? Log in
Subscribe to read the full story →
Smart Quarterly
₹900
3 Months
₹300/Month
Smart Essential
₹2,700
1 Year
₹225/Month
Super Saver
₹3,900
2 Years
₹162/Month
Renews automatically, cancel anytime
Here’s what’s included in our digital subscription plans
Exclusive premium stories online
Over 30 premium stories daily, handpicked by our editors


Complimentary Access to The New York Times
News, Games, Cooking, Audio, Wirecutter & The Athletic
Business Standard Epaper
Digital replica of our daily newspaper — with options to read, save, and share


Curated Newsletters
Insights on markets, finance, politics, tech, and more delivered to your inbox
Market Analysis & Investment Insights
In-depth market analysis & insights with access to The Smart Investor


Archives
Repository of articles and publications dating back to 1997
Ad-free Reading
Uninterrupted reading experience with no advertisements


Seamless Access Across All Devices
Access Business Standard across devices — mobile, tablet, or PC, via web or app
