Giving your home a thorough pressure wash can be quite miraculous for you, and a big part of the reason why that is the case has to do with the fact that it would get rid of dirt that you might not even have been aware of the existence of at any given point in time. The thing is, it is usually never going to be all that good of an idea to hire a service without first and foremost developing a baseline understanding of what it is they do and how they go about fulfilling your requirements in whatever way, shape or form you ask of them.
The first thing to know about a power washing company that you might hire is that they will often use chemicals during the process. Suffice it to say that straight water washing will do very little to kill bacteria, and it will fail to rid your home of dirt patches that are more on the stubborn side of the spectrum. Hence, it is a very good thing that these companies use as many chemicals as they do, because it reveals that they are committed to giving you a good experience.
These companies usually use sodium hydrazine in most situations because of its potency as a degreasing agent. The chemical composition of this substance makes it so that grease will start to melt away as soon as it comes in contact with it, so the lipid particles that had accumulated on the exterior of your house will get washed off without a single ounce of effort being required on your part. This is just one of the many chemicals that are used.