Chemical Gases: Ethylene Oxide, Ozone, & Formaldehyde - Online Tutor, Practice Problems & Exam Prep

Ethylene oxide, a highly flammable and potentially carcinogenic gas, is effective in sterilizing materials, including heat and moisture-sensitive items. It requires long treatment times and must be used in specialized chambers to control temperature, humidity, and gas concentration. Formaldehyde, available as a gas or in a 37% aqueous solution (formalin), kills microbes by cross-linking proteins and DNA, leading to cellular damage. Ozone (O₃), a strong oxidizing agent, decomposes quickly and is generated on-site for microbial control, often used in water disinfection. Each gas presents unique advantages and safety considerations in microbial growth control.

Chemical Gases: Ethylene Oxide

In this video, we're going to begin our lesson on chemical gases for controlling microbial growth, specifically ethylene oxide, ozone, and formaldehyde. Now in this video, we're only going to focus on ethylene oxide, but moving forward in our next lesson videos, we'll talk about ozone and formaldehyde. Ethylene oxide is a highly flammable and potentially explosive gas sterilizer, meaning that it's capable of killing all microbes, including endospores, which are really resistant. Although ethylene oxide is a gas sterilizer capable of killing all microbes, it does require really long treatment times, which is a slight disadvantage. Another disadvantage of ethylene oxide is that it is potentially carcinogenic, meaning that it is capable of contributing to the development of cancer. Therefore, because it is highly flammable, potentially explosive, and carcinogenic, it must be removed from the sterilized material after treatment with ethylene oxide. The ethylene oxide is removed by forcing out the ethylene oxide with air.

Sterilization via ethylene oxide treatment must be carried out in a specialized chamber in order to control variables such as temperature, humidity, and the concentration at which the ethylene oxide gas is used. These variables are important and can affect the use of ethylene oxide. Notice down below we're showing you an image of ethylene oxide. Over here on the left-hand side, we're showing you the chemical structure of ethylene oxide. This is a very dangerous, highly flammable, potentially carcinogenic, and explosive gas, and so it must be carried out in a specialized chamber as you see here. This is the ethylene oxide treatment chamber.

One of the good uses of ethylene oxide is that it is a gas, it is highly penetrative, which means that it can penetrate into things that might be difficult to reach otherwise. It can get into mattresses, for example, or pillows, basically areas that might otherwise be difficult to reach. Because ethylene oxide is a gas, it can reach these areas that are difficult to reach. It's also good for treating materials that are heat sensitive and moisture sensitive, such as electrical equipment. Ethylene oxide is a method that is used to control microbial growth in some scenarios.

This here concludes our brief lesson on ethylene oxide as a chemical gas for controlling microbial growth. As we move forward in our course, we'll be able to apply these concepts, and we'll also get to talk about ozone and formaldehyde gases. I'll see you all in our next video.

Ethylene oxide is gas that:

• A. Requires special conditions when being used.
• B. Is potentially carcinogenic.
• C. Is used as a 37% aqueous solution.
• D. Is effective against all microorganisms except endospores and viruses.
• E. A and B.
• F. C and D.

Formaldehyde Gas

In this video, we're going to talk about yet another chemical gas used for controlling microbial growth, and that is formaldehyde gas. And so formaldehyde gas is a colorless, strong-smelling aldehyde in a gas form that is made by oxidizing a chemical called methanol, whose chemical formula is CH₂O. Now formaldehyde gas can actually be used as a disinfectant at a 3% dilution, or it could be used as a sterilant at a higher concentrated form of a 37% solution. Although formaldehyde is available in a gas form, it's also commonly available in a 37% aqueous solution or a liquid form that is called formalin. And so formalin is really just the liquid version of formaldehyde. Now, whether you're using formaldehyde gas or this liquid form of formaldehyde, formalin, it is going to kill microbes by causing protein DNA cross-linking, basically covalently linking proteins to DNA. And this cross-linking will eventually damage the DNA and denature proteins. And of course, damaging the DNA and denaturing proteins can lead to the destruction of the microbe, allowing formaldehyde gas and formalin to be used to control microbial growth.

And so if we take a look at this image down below, we're focusing in on formaldehyde as a gas. And over here we're showing you the chemical formula and the chemical structure of formaldehyde. And over here what we have is a little bottle that can contain the liquid version of formaldehyde, the formalin aqueous solution. And so the use of formaldehyde gas or this liquid formalin form of formaldehyde will lead to the same result. And so the formaldehyde is able to diffuse across a cell's plasma membrane here, and it's able to interact with proteins that are found inside the cell. It's also able to interact with the DNA that's found inside the cell as well. And so it can cause these DNA-protein cross-links, basically covalently linking the protein to the DNA, and that can again, damage the DNA and denature proteins, leading to the destruction of the microbe.

This here concludes our brief lesson on the use of formaldehyde gas as a means for controlling microbial growth. And we'll be able to get some practice applying these concepts and then learn about ozone in our next lesson video. So I'll see you all in that video.

___________ is the commercially available form of formaldehyde in a 37% aqueous solution.

• A. Aldehyde.
• B. Formalin.
• C. Methanol.
• D. Hydrogen Peroxide.

Ozone

In this video, we're going to briefly discuss yet another type of chemical gas used for controlling microbial growth, and that is ozone. Ozone actually has a chemical formula of O3, and if we take a look at our image down below, notice that on the left-hand side over here we're showing you the chemical structure of ozone. Ozone is a very unstable form of oxygen and can serve as a strong oxidizing agent, which means it can cause other molecules around it to become oxidized or to lose electrons.

Because ozone is so unstable, it is also going to be very highly reactive, and so ozone can react to form free radicals, which are also very reactive molecules and are also very dangerous to cells because free radicals can lead to cell lysis or cell rupturing, causing the cell to die. This is how ozone can be used as a method of controlling microbial growth because it can lead to cell lysis. Again, because ozone is so unstable and so highly reactive, it is going to decompose very quickly. Because it decomposes so quickly, it means that ozone must be generated on-site with a generator in order for scientists to use the ozone as a method of controlling microbial growth.

Notice that down below in our image on the right-hand side, we're showing you an ozone generator. Ozone is often used as an alternative to chlorine for disinfecting water, including drinking water. Thus, ozone is going to be a very important method of controlling microbial growth in certain circumstances. If we take a look at our image down below again, in the middle, we are actually showing you an image of our atmosphere because ozone plays a role in the atmosphere to help protect us from UV light that comes from the sun or ultraviolet light that comes from the sun.

But this here concludes our brief lesson on ozone and its use as a method of controlling microbial growth, and we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video.

Which of the following statements about ozone is FALSE?

• A. It can be used to disinfect drinking water.
• B. It is a strong oxidizing agent.
• C. It causes cell lysis when free radicals form in water.
• D. It is a surfactant.