The use of masks and smart cards has been made mandatory as the Delhi Metro resumes services next month after a five-month gap. The new guidelines issued by the Delhi government today listed severe restrictions that included a ban on tokens for the train ride and limiting the number of passengers in each coach. The authorities, however, have not named a figure for this yet. The air conditioning system will also be "renovated" to ensure circulation of fresh air inside coaches, said Delhi Transport minister Kailash Gahlot.