Always stick to a strict schedule wherein you clean your carpet every month at least twice. It is an indispensable part of hygiene programme even though it seems a daunting task. Fine dirt and grit from outdoor surfaces, residual oil from cars and factories, sand chemicals, are just a few reasons which makes your carpets dirty. With scores of people treading these carpets everyday and every spilling that comes its way often ends in stale odor and erodes the strength of the fibres. One way to reduce the burden is to provide protective floor mats around high traffic areas, food court , coolers, doorways. I guess that will bring some respite to the frequency of cleaning which has to be done . There are many commercial cleaning services for carpets in the market like the Royal Building Cleaning Limited which offers professional cleaning services.