Formaldehyde detecting device

A formaldehyde detecting device, comprising:

• a formaldehyde detecting unit that has a first surface through which formaldehyde enters, a second surface opposite to said first surface, and a lateral surface interconnecting said first surface and said second surface, said formaldehyde detecting unit including
• a formaldehyde detecting layer having said second surface and a formaldehyde detecting surface opposite to said second surface, said formaldehyde detecting layer including a formaldehyde detecting material that is applied on said formaldehyde detecting surface and that develops color when reacting with formaldehyde;
• a diffusion restricting member that covers a portion of said formaldehyde detecting surface, and that is configured to permit a restricted amount of formaldehyde to pass therethrough to react with said formaldehyde detecting material on said portion of said formaldehyde detecting surface, in such a manner that concentration of formaldehyde is determined based on a color change on said portion of said formaldehyde detecting surface;
• and
• a concentration indicator that is disposed on at least one of said formaldehyde detecting surface and said diffusion restricting member, and that is configured to indicate the concentration of formaldehyde detected;
• and
• a formaldehyde barrier unit covering said lateral surface and said second surface of said formaldehyde detecting unit to avoid formaldehyde entering said formaldehyde detecting unit through said lateral surface and said second surface.