The manufacturer of a new type of air mask, which has been the subject of complaints from Baltimore firefighters for a year, has been ordered by the National Institute for Occupational Safety and Health to correct deficiencies in the apparatus.

The Baltimore City fire department purchased the positive-pressure air masks from Clifton Precision a year ago, but locals 734 and 964 of the International Association of Firefighters complained about several deficiencies in the masks, which prompted NIOSH to order the corrections.

The positive-pressure air mask is among the most advanced breathing devices available because it conforms to a person's facial features and prevents the inhalation of toxic fumes. Air is automatically pumped into the mask. Older masks required users to breathe the air in themselves.

NIOSH also ordered fire departments and agencies using the newer masks to provide additional training for their use and maintenance. The agency will continue to study the problems.

Since the masks were first used in Baltimore, firefighters have lodged more than a dozen official complaints with the fire department and unofficial complaints with the union. Firefighters have complained the masks fall apart and that users have been left without air in their tanks.