Firefighters worked through the night to bring the blaze under control after it began just after 9pm at the intersection of Seventh Avenue and Beaufort.
Zoran Blagaich was with his girlfriend at nearby markets when he heard someone shout “fire”.
“My natural instinct was to go and help so I started jumping fences and there were people screaming in their backyards,” he said.
“Next thing you know I was on the other end of a hose with exploding stuff on the other side of the fence.”
An Inglewood resident described Mr Blagaich’s actions as heroic but he downplayed his bravery.
“The heat was intense, there was corrugated iron burning right in front of me, stuff was exploding.”
“It was dangerous but I just went for it, the Aussie way.”
Witnesses say they heard loud explosions for almost an hour after the blaze broke out.
Bunnings is known to stock a wide variety of chemicals, paints, building materials and other potentially hazardous and toxic liquids.
A Department of Fire and Emergency Services spokesman said the blaze is now contained and controlled but firefighters would remain at the scene throughout the day.