A team from the Healthcare Environment Inspectorate made an unannounced visit to Western Infirmary in Glasgow in August and found that there was no time-scale in place yet for when a Legionella policy will be implemented.
Inspectors were told on a previous visit to the hospital in 2011 that NHS Greater Glasgow and Clyde's policy for Legionella, the bacteria that causes Legionnaires' disease, was under review and due to be formally approved.
But minutes from a meeting in July this year suggested "no decision had been made on when the draft policy will be approved", the inspectors said.
The health board has now been given a month to provide a time-scale for when a Legionella policy will be approved and implemented.
NHS Greater Glasgow and Clyde has also been told to ensure staff on the hospital wards follow the isolation policy, after inspectors noticed a number of isolation rooms had their doors left open.
This "may pose a particular risk of cross-infection to other patients, staff and visitors", the inspectors warned as they pointed out that in July last year the health board was told to ensure the isolation policy was implemented, with monitoring to be carried out of whether doors to isolation rooms were left open.
Their report also revealed that some bins for staff to dispose of sharp equipment were not assembled or labelled correctly and were sometimes not closed properly.
A container for used linen was open when the inspectors visited, instead of being stored in a locked area while awaiting removal.
But overall, NHS Greater Glasgow and Clyde is making good progress on standards to protect patients, staff and visitors from the risks of catching an hospital infection, according to the inspectors.
"Staff demonstrated good awareness, knowledge and understanding of their roles and responsibilities for infection prevention and control, and patient equipment was clean. However, there are a number of areas for improvement including two requirements that have not been met from our previous inspection," chief inspector Susan Brimelow said.
"We expect NHS Greater Glasgow and Clyde to address these areas as a priority."
Rory Farrelly, the health board's acute director of nursing, said: "We have received the inspector's report and are disappointed that some areas are still falling short of the standards expected in all our hospitals.
"Clearly we need to reinforce some of our policies with staff, including the disposal of sharps, storage of linen and our Legionella policy which, like all our policies, is available to staff on our intranet."
An action plan has been drawn up to address the requirements and recommendations of the report, he said.
"We are pleased that Susan Brimelow, HEI chief inspector, 'recognised that staff demonstrated good awareness, knowledge and understanding of their roles and responsibilities for infection prevention and control, and patient equipment was clean'."