High Risk, Harsh and Hazardous Environments” are where security is frequently deployed. These terms are sometimes used casually, and for good reason. These expressions are now assimilated into culture and the security industry. They are used to describe a wide variety of situations and conditions.
The strongest threat posed from the three is “hazardous.” It appears in the NFPA (National Fire Protection Association) code and has a clear definition. A “hazardous environment” is typically one that contains amounts of explosive gases or dust either during normal operations or during an abnormal circumstance. These areas are frequently found in petrochemical, chemical, pharmaceutical and painting industries where hazardous substances are by-products or the end product of the normal process. The word hazardous is further defined by the NFPA under a Class, Division, Group rating system which helps define the severity of the hazardous environment.
CLASS: Defines the form of hazardous substance present.
1. Class I - Area where ignitable concentrations of flammable gases or liquid vapors are present.
2. Class II - Area where ignitable concentrations of combustible dusts are present.
DIVISION: Defines the level of hazardous substance concentration.
1. Division 1 - Hazardous substances are present during normal operation.
2. Division 2 - Hazardous substances are present only during abnormal conditions (such as a leak).
GROUPS: Defines the type of hazardous substance.
1. Class I Substances
Group A – Acetylene (most volatile).
Group B – Hydrogen.
Group C – Ethylene.
Group D – Methane.
2. Class II Substances
Group E – Conductive (Metal) Dust (Automatically classified as Division 1).
Group F – Carbonaceous (Carbon or Coal) Dust.
Group G – Agricultural (Flour or Grain) Dust.
Types of Protection
The three types of protection available are:
1. Intrinsic Safety – This is a means of limiting the amount of energy that a particular piece of electrical apparatus generates or stores. These voltage levels are typically in the 5 to 24 Volt range and are associated with annunciators, instrumentation and other “light load” electrical equipment.
2. Explosion Proof Enclosures – These enclosures are designed to contain an explosion as opposed to preventing one. They’re constructed of heavy cast iron material and have limited openings and, therefore, limited access. Heavy duty electrical apparatus that requires minimal interface are many times housed in these enclosures which tend to be somewhat bulky and cost prohibitive.
3. Purging Technology – The third form of recognized protection by the NFPA is purging. This concept basically means that a NEMA 4/4X rated enclosure will be pressurized with an inert (non-explosive) gas such that the internal pressure of the enclosure is greater than the external pressure of the environment. Consequently, there will always be a continuous clean air flow out of the enclosure thereby preventing the intrusion of explosive gases or dusts into the enclosure.
“High Risk, Hazardous and Harsh Environments” represent both the issues addressed in the above definition, as well as sociological phenomenon which affects the occupants of the premises you protect, the equipment you install and your installers themselves. Criminal elements, difficult installation environments, temperature extremes, etc. fall into these broad categories used when specifying and installing systems.
Wireless equipment helps mitigate several factors which contribute to hazardous, high risk and harsh conditions. One reason is that the usual methods of running wire, which might involve ladder work or trenching, is mitigated. This technology, often times, is able to provide levels of reliable security which may exceed the hardwired counterpart by virtue of the strategic deployment possible with wireless.