Although you may be within the acceptable limits for OSHA's established PEL and STEL for formaldehyde but there is also an OSHA "Action Level" of .5 ppm. Do you know whether or not you are below this action level?
Either way, René brings up a good point that these are guidelines and not all individuals are created equal. OSHA bases these "acceptable" permissible exposure limits on an exposed worker being a "healthy male adult weighing 150 lbs". Based on this employee's medical predisposition of asthma you should make every effort to remove them from a situation where they would exposed to any hazardous substance that would potentially make them ill because of their medical problem. Also since this person has a medical illness that affects their breathing additional personal protective equipment (e.g. respirator) will most likely not work as the medical professional evaluating their medical questionnaire for respirator clearance would clear them based on their medical history. As a standard practice you should always use administrative (e.g. procedural modifications) and engineering controls (e.g. ventilated workspaces) to minimize any employee occupational exposure to a hazardous material before implementing personal protective equipment.
Finally I would review the situation with your chemical hygiene officer and/or EHS department to help come up with a solution and avoid any non-compliance or possible legal ramifications of not providing a safe workplace.
I hope this helps.
Sr. Manager, Histology and Laboratory Safety
Charles River Laboratories
251 Ballardvale Street
Wilmington, MA 01887
**Please note new direct dial telephone number**
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