Well, this is the main question isn't it? There is no simple answer because every situation is different, such as: How much laundry do you do? How loing is the dryer vent system, is it 5 feet or 40 feet long? Is there a screen on the termination point? All of these questions factor in on how often you should have your dryer vent system cleaned. A good rule of thumb is to check the system every six months and clean if required but at least once per year for a full cleaning.
When your dryer is in operation it is producing large amounts of heat, and becasue your clothes are wet going into the dryer there is going to be alot of humidity. With that being said your laundry room should not experience barely any added heat or humidity unless there is a problem with your venting. Check to make sure the dryer venting is hooked up at the back of the dryer first, many times the venting gets disconected when moving the dryer and then you are simply venting into the laundry room.
It certainly can be. There are alot of dryer fires every year in North America and the main cause is a plugged dryer exhaust system. Dryer exhaust is meant to take hot, humid air to the outside of the building, but if the venting is plugged and the air can't escape the heat will build up and potentially cause a fire.
The venting that connects your dryer to the dryer venting system should be 4" in diameter, fully round without any damage, short as possible, and as few bends and angles as possible. Anytime that these requirements are not met it means lower airflow which can mean longer dry times, clogged venting, and potential fire hazards.
You want to keep a minimum of six inches of space between the wall and the back of the dryer. This allows enough space for the venting to be placed without crushing it. If you don't have alot of room you can have products such as The Dryer Box installed in the wall that helps gain some space and prevents the ducting from getting crushed.
The dryer vent termination point shopuld be free of all obstrucstions, including lint, birds nests, and any screening material for keeping rodents out. Screening that has clogged up is one of the top reasons that we get called out for dryer vent repair services. Screens are against Alberta building code and can create a real hazard.
Many new dryer's are equipped with a air flow sensor that will warn you that the dryer is having a problem exhausting like it should. This can be caused be a few different situations such as a lint screen that needs cleaning, a plugged dryer vent system, or a dryer vent termination point that is plugged up. Start with the simple stuff and make sure that your lint screen is clean and the termination point is free of all debris.
M1502.6 Duct length.
The maximum length of a clothes dryer exhaust duct shall not exceed 25 feet (7,620 mm) from the dryer location to the wall or roof termination. The maximum length of the duct shall be reduced 2.5 feet (762 mm) for each 45-degree (0.8 rad) bend, and 5 feet (1,524 mm) for each 90-degree (1.6 rad) bend. The maximum length of the exhaust duct does not include the transition duct. M1502.2 Duct termination.
Exhaust ducts shall terminate on the outside of the building or shall be in accordance with the dryer manufacturer’s installation instructions. Exhaust ducts shall terminate not less than 3 feet (914 mm) in any direction from openings into buildings. Exhaust duct terminations shall be equipped with a backdraft damper. Screens shall not be installed at the duct termination.
Dryer vent hose is relativly easy to hook up to a dryer, but there are a couple of ways to make it easier. First your dryer venting is going to be 4" in diameter at both the back of the dryer and at the wall where you connect to the dryer vent system. Pick up to adjustable hose clamps that are 4" in size at the hardware store, make sure to use good semi ridgid aluminum ducting, not cheap plastic stuff. Cut a length of the 4" tubing just long enough to make the connection at both ends and give yourself the ability to pull the dryer out a couple feet without it becoming disconnected. Slip the 4" clamps over each end of the tubing and connect the wall connection first, push the dryer away to the maximum distance allowed by your cut tubing and then connect it to the back of the dryer. Try to keep this connection as straight as possible. Now plug your dryer in, turn it on and check for any leaks, if you need to, you can apply heat foil tape to prevent any leaks. After the check is done, turn the dryer off and climb out from behind the dryer and slowly push it back towards the wall, be careful not to allow any un-neccessary twists and turns that will slow down the airflow. Make sure to leave at least 6" of space between the wall and the back of the dryer.