Coal mining generates significant adverse environmental impacts. Historically, coal mining has been a very dangerous activity and the list of historical coal mining disasters is a long one. Underground mining hazards include suffocation, gas poisoning, roof collapse and gas explosions.
The term 'OVD' (Optically Variable Device) is used to describe both laser generated hologram images and electron beam generated images. These optically variable devices are created in highly-secure facilities and are at the forefront of overt asset and brand protection programmes.
NonVisual Desktop Access (NVDA) is a free and open source screen reader for the Microsoft Windows operating system developed by NV Access, with contributions from the community. It can be downloaded from NV Access. This page only lists a few of the most used keyboard short-cuts and commands, for a complete list See NVDA User Guide. The NVDA Modifier Key. Most NVDA-specific keyboard commands consist of pressing a particular key called the NVDA modifier key (Numpad Insert or Extended Insert by default) in conjunction with one or more other keys. In the table below, this will be referred to as just NVDA.