I am a commercial cleaning contractor new to this forum. Belated Happy Thanksgiving to everyone. I received a call this morning from one of my clients, saying that several of their employees, herself included were experiencing several symptoms ranging from scratchy throats, itchy eyes, to a metallic taste in their mouth. She called me to see if we had used anything different in our cleaning process. The answer was no. we also looked for any open containers around the HVAC system, nothing. Do you have any ideas?