SB 3.28.40

yatholmukād visphuliṅgād
 dhūmād vāpi sva-sambhavāt
apy ātmatvenābhimatād
 yathāgniḥ pṛthag ulmukāt
Synonyms: 
yathā — as; ulmukāt — from the flames; visphuliṅgāt — from the sparks; dhūmāt — from the smoke; — or; api — even; sva-sambhavāt — produced from itself; api — although; ātmatvena — by nature; abhimatāt — intimately connected; yathā — as; agniḥ — the fire; pṛthak — different; ulmukāt — from the flames.
Translation: 
The blazing fire is different from the flames, from the sparks and from the smoke, although all are intimately connected because they are born from the same blazing wood.
Purport: 

Although the blazing firewood, the sparks, the smoke and the flame cannot stay apart because each of them is part and parcel of the fire, still they are different from one another. A less intelligent person accepts the smoke as fire, although fire and smoke are completely different. The heat and light of the fire are separate, although one cannot differentiate fire from heat and light.