Intro

In this lesson, we finish our look at physical security by exploring how to minimize the risk of data center environmental factors interrupting critical business functions. These factors include temperature and humidity control and fire suppression. You can download the script for this video from above or at the end of the video. Three environmental control categories are important considerations for maintaining data center health: temperature, humidity. and fire suppression. In addition to implementation, each of these must be monitored and regularly checked for proper operation.

Temperature

Heating is not a problem or consideration for the vast majority of data centers. Rather, mitigating the heat produced by the devices themselves is the primary consideration. This example shows a recommended approach to data center design. The rack rows are configured so that in each set of two rows the racks are designed so that the fronts of the racked devices face each other. This enables the creation of a cool row created with perforated tiles on the data center's raised floor. All other floor tiles are unperforated, and all gaps and flooring are blocked. This focuses cooling airflow to the cooling rows. The cool air is drawn in by rack device fans, and the heated air exits into a heated row. The air in the heated row cycles back to the cooling system. There are various temperature and humidity recommendations based on the type of equipment protected and its criticality. The american society of heating refrigerating and air conditioning engineers or ASHRAE recommends keeping data centers between the temperature range of 64.4 to 80.6 degrees Fahrenheit to address temperature requirements for all types of equipment in the data center. The table shown depicts the equipment types and the temperature and humidity requirements for each. In addition to cooling, data center humidity must also be controlled. Humidity levels are also determined by the types of equipment present.

Humidity

The ASHRAE recommends a relative humidity of about 60 percent to address all types of equipment.

Fire Risks

Like with any security control, we need to understand both risk and management's risk appetite. This allows the selection of the right fire suppression system with a reasonable and appropriate total cost of ownership. Things to consider include human safety, which is the most important consideration, and costs. Costs include loss of business functionality, replacement of equipment and facilities, and it also includes the purchase cost and implementation of the suppression system and the associated regular maintenance of that suppression system.

Fire Basics

At its most basic level, a fire requires three elements, as shown in this common triangle model: air or oxygen, heat, and fuel. Removing one of these prevents a fire from starting or it allows suppressing an existing fire. Fire suppression systems are typically designed to remove either air, heat, or as we'll see in a later slide, the chemical reaction that perpetuates the fire.

Water Suppression Systems

Water systems are the most common in business environments. There are four types: wet pipe, dry pipe, deluge, and pre-action. We use water to remove HEAT from a fire.

Wet-pipe Systems

Wet pipe systems are the most commonly used. The pipes leading to ceiling valves are always filled with water. When a fire causes the valves to experience a certain level of heat, the valves open. The advantages of wet pipe include low cost for installation and maintenance. They're also highly reliable and only release water closest to the fire. The problem with wet pipe is the damage water does to computer equipment, and this is the problem across all water based fire suppression systems. Damage can be caused by the actual release due to fire, pipe condensation, or a defective valve. Dry pipe systems are similar to wet pipe in design and the delivery of water to fire locations. The primary difference is the lack of water in the pipes feeding the valves until a fire is detected with heat, smoke, or with a manual alarm. The advantage is the lack of accidental water release due to condensation or valve failure. The disadvantages include increased time to water release onto the fire. Further, empty pipes might have an increased chance of corrosion.

Deluge Systems

Deluge systems are constructed like dry pipe but with all valves always open. Instead of water being delivered only to the location of the fire, it's dropped over an entire area. An example would be a plant floor where fire spread must be controlled.

Pre-action Systems

Pre-action systems have an extra step in the distribution of water. For example, a pre-action dry pipe system would have an initial trigger that would fill the pipes with water, but the water would not be released through the valves until an additional trigger occurred.

Mist Systems

Finally, any of these water systems can have a different sprinkler head that creates a mist as a delivery mechanism. In addition to removing heat from the fire, the steam created when the mist reaches the fire also displaces oxygen, so mist delivery systems remove both air and heat from a fire.

Chemical and Gas Suppression

Because water can cause significant damage to data center equipment, chemical and gaseous methods of fire suppression were developed. The first two were halon and carbon dioxide. Halon interferes with the chemical reaction that causes fires to continue. I show this better in the next slide. Carbon dioxide interferes with the chemical reaction and removes oxygen from the air. Both work well, and they might still be found in some data centers. However, the disadvantages associated with both have caused their removal from suppression solution offerings. For example, if humans are in a data center when a carbon dioxide system initiates, there's a chance of asphyxiation because of the lack of oxygen. Halon damages the environment. Three examples of replacements for halon and 100 carbon dioxide deployments include hhc227ea, fluorinated ketone, and gas mixtures. As with earlier solutions, these approaches interfere with chemical reactions or remove oxygen. None of these approaches are generally harmful to equipment. However, some solutions require cleanup after release.

Fire Tetrahedron

Let's take a quick look at chemical reaction interference. This is the traditional fire triangle we looked at previously, also used in the fire tetrahedron. The tetrahedron includes air, heat, and fuel with the addition of the chemical reaction that perpetuates the fire. Interfering with the reaction destroys the ability of the fire to feed itself.

Fire Extinguishers

Fire extinguishers in the workplace are governed by laws and regulations. They're not intended to put out fires, although they might work for small fires like those that start in someone's trash can. Instead, extinguishers are intended to clear paths for humans to exit areas threatened by fire or smoke. The type of extinguisher required and its placement is governed by established standards.

Extinguisher Types and Placement

This table shows the types of extinguishers and when they should be used. Also, the maximum distance a person should have to travel to each type of extinguisher is listed in column 3. Type C extinguishers are type A or B extinguishers that are also rated for electrical fires. Well, that's it for this lesson. If you have questions, please ask. ...and until next time be careful once you click.