Carbon monoxide is a very dangerous gas for human beings. It is extremely toxic yet it is invisible and odourless making it even more dangerous as it can only be detected by measuring devices. CO is formed as a result of incomplete combustion of carbon fuel e.g. gas/coal. It may be formed due to a lack of air, too much excess air or flames cooling to quickly. It can get into rooms via defect, badly maintained, falsely adjusted heating systems. Just 0.16% (1600ppm) can lead to death within 2 hours and only 1.28% (12800pp,) can cause death within 1-3 minutes. Thus it is highly important that concentrations are measured often and thoroughly.

Humidity is the amount of water vapour in an air sample. There are three ways to measure humidity. Absolute humidity which measures how many grams of water are in a cubic meter of gas or air. It is the most frequently used measurement as it is often used in weather forecasts because it can help estimate the likelihood of rain, dew or fog. Secondly relative humidity measures the percentage of maximum water vapour currently in the air. The greater the relative humidity hotter it may appear to be as it reduces the effectiveness of sweating to cool the body. Finally specific humidity is the ratio of water vapour to air in a particular volume of air.

The concentration of carbon dioxide is used as an indicator when assessing indoor air quality. The limit value for CO₂ is 1000 ppm, if levels are too high it can make the air “stuffy or stale” Rooms with poor air quality may result in tiredness and a lack of concentration or even in some cases illness otherwise known as sick building syndrome (SBS). Symptoms include: headaches, eye, nose and throat irritation, itchy skin, nausea, dizziness, fatigue and difficulty concentrating.

Within our daily life all bodies give off radiation or electromagnetic waves dependant upon their temperature. Energy is transported during this dispersion of radiation and this energy allows us to use radiation as a measurement for body temperature without actual contact. This can be done because the energy & Its characteristic wavelengths are dependant on the temperature.

Photometry is the science of measurement of visible light in terms of its perceived brightness to human vision. Light can be measured in several ways. Two of the most frequently used methods used in industry include Lux and foot-candles. Lux (lux) is a unit of illumination of one square metre which is one meter away from a uniform light source. One lux is equal to one lumen per square meter.

pH is the measurement of hydrogen ion concentration in a liquid solution. This activity is directly connected to its acidic, neutral or alkaline characteristics. If a solution has a pH of less than 7 (a large number of Hydrogen ions) it is considered acidic. Those solutions with a pH of 7 are considered neutral as is the pH of pure water at 25°C. Anything with a pH of above 7 (a small number of hydrogen ions) is considered alkaline. The pH scales reads from 1 (acidic) to 14 (alkaline) Sometimes it is possible to come across solutions that may have a pH of below 0 or above 14 however this is very rare and any solutions that are, are concentrated and highly reactive.

Temperature can be measured in two ways, by either contact measurement or non contact measurement. The method you need to use will depend on the application you are using it for, you may need either or a combination of both. When measuring temperature there are several different probes you can choose from. The choice of probe will be determined by the measuring task. Probes are selected by using the following criteria.