Take an example of reaction like :
Burning of carbon in air to form Carbon dioxide, say heat required is 100 joule (assume so) And we provide the system say 20 joule heat Theoretically it would be not possible. But the alone C atoms present near heat source will absorb their required heat (which would be very very small indeed) and get converted into co2 Hence, there will be small value of reactants which are converted into products then how can we say reaction is not possible. Thus at room temperature is it true that there is some concentration of products in any reaction.