Abstract: A shelter to protect users from an external environment has an inner front module having an airlock and an outer front module which is slidingly attached to the inner front module. The shelter has an inner rear module and an outer rear module slidingly attached to the inner rear module. When the outer front module and the inner front module are in an extended state and the outer rear module and the inner rear module are in an extended state and the outer front module and outer rear module are attached, they form an airtight chamber in which users are protected from the external environment. A method for constructing a shelter to protect users from an external environment is also disclosed.

Abstract: A shelter to protect users from an external environment has an inner front module having an airlock and an outer front module which is slidingly attached to the inner front module. The shelter has an inner rear module and an outer rear module sliding attached to the inner rear module. When the outer front module and the inner front module are in an extended state and the outer rear module and the inner rear module are in an extended state and the outer front module and outer rear module are attached, they form an airtight chamber in which users are protected from the external environment. A method for constructing a shelter to protect users from an external environment.

Abstract: A filtering apparatus (50) for removing noxious gases from an environment including: a source of compressed gas (60) connected to a regulating valve (62) to regulate a supply of compressed gas; at least one airflow device (5) including a compressed gas inlet (10) for receiving gas from the supply of compressed gas at greater than ambient atmospheric pressure, the gas inlet (10) being operably connected to the regulating valve (62); and a permeable noxious gas filter (55) arranged in gaseous communication with the airflow device (5); wherein the supply of compressed gas to the airflow device (5) causes the airflow device (5) to draw ambient air (64) from the environment through a primary intake (42), thereby generating a flow of air through the noxious gas filter (55) and causing the substantial removal of noxious gases from the flow of air.

Abstract: A ranged precision voltage monitor with out-of-range enunciator characterized by a power supply and reference voltage stage, a voltage sensing stage, and an enunciator stage. The power supply stage provides power for the monitor, and further provides a reference voltage and a sensing voltage. The voltage sensing stage senses and displays voltage levels within a predetermined range, and further senses and displays over-range and under-range conditions. The enunciator produces a first audible tone for under-range conditions, and a second audible tone for over-range conditions.