A habitat is

• the natural home of an animal or plant;
• the sum of the Environmental conditions that determine the existence of a Community in a specific place.

A Hazard Index (HI): is the sum of hazard quotients for substances that affect the same target organ or organ system.

A Hazard Ranking System (HRS) is the method EPA uses to assess and score the hazards posed by a site that takes into account the nature and extent of Contamination and the potential for the hazardous substances to migrate from the site through air, soil, surface water, or groundwater; HRS scores are used to determine whether a site should be placed on the National Priorities List (NPL)

The Hazardous Air Pollutant Exposure Model, Version 4 (HAPEM4) is a computer model that has been designed to estimate inhalation exposure for specified population groups and air toxics.

A Hazardous and Solid Waste Amendments (HSWA) is amendments to RCRA,

A Heat Pipe is a device that can quickly transfer heat from one point to another.

The Historical Data are data sets from previous studies, which can range from handwritten field notes to published journal articles.