The HMIS has undergone several revisions since it was developed. The color-coding and numeric rating system correspond to that established in NFPA 704; however, HMIS expands the white section (i.e., protective equipment) further than NFPA 704. An alphabetic code system was developed to provide PPE requirements to personnel.

• A – Safety glasses
• B – Safety glasses and gloves
• C – Safety glasses, gloves, and apron
• D – Face shield, gloves, and apron
• E – Safety glasses, gloves, and a dust respirator
• F – Safety glasses, gloves, apron, and a dust respirator
• G – Safety glasses, gloves, and a vapor respirator
• H – Splash goggles, gloves, apron, and vapor respirator
• I – Safety glasses, gloves, and a dust and vapor respirator
• J – Safety goggles, gloves, apron, and a dust and vapor respirator
• K – Airline hood or mask, gloves, full suit, and boots
• X – Consult your supervisor or SOG (standard operating guide) for special direction