Almost had a close one yesterday morning.  I work nights and sleep in the day.  I went to bed around 0500 (my off day) and awoke around 0930 to my dog Jake, growling and hair on end.  "OH SHIT" I summise (Knowing Jake is a freindly dog and doesn't do that unless SHTF) and get 1/2 out of bed when I hear the front door downstairs openning!
I grabbed my Beretta 96G EI w/ M3 and cellphone then start down the stairs (cutting the corners) when I hear knocking on the door.
That threw me off.  Who would break into a house and announce there presence?  So I yelled out (from a covered, elevated position<and in my best BADDASS voice>)"WHO IS IT?"
"Repair man." is the responce I get.
"Wait on the front porch and close the door so I can put my dog away." I order never taking my eyes off the front sight.  I hear the door close so I grabbed some clothes (Yes, I was)  and open the door when I get settled.
"Can I help you?" I ask.
"I need to replace the air filter upstairs." he says.  He is not wearing a uniform (didn't expect him to) and had no ID markings on his truck.  He did have a step ladder and an air filter.  I don't know this guy from Adam.
"I just replaced it when I moved in, 4 months ago, it's fine and I have an exta filter."  Why didn't they call me?"
He just shrugged, and mummbled something I didn't catch.  I took the filter with my left (He never saw my right because it had a firearm in it and was behind the door)and thanked him for coming by.  Wasn't his fault after all.  
I double checked my Lease and sure enough....24 hour WRITTEN notification is manditory for ANY unrequested repairs that require entry!  I didn't bother telling the guy how close he came to getting 2 in the chest or used as a chew toy.

Any similar circumstance or stories like this?

You need to calm down a bit, or is every person that knocks on your door in lethal danger?

Quoted: You need to calm down a bit, or is every person that knocks on your door in lethal danger?

Eh, can't totally blame the guy.  Better paranoid than dead.  He didn't fire and he kept the gun out of sight.  No harm, no foul.  And they really should've notified you, as well as having the person wear something close to a uniform or some kind of ID, and the truck really should've been marked.  I had a similar encounter at my parents' townhouse when I lived with them.  My parents own the house.  My mom woke me up at 11am to tell me there were strange men on our deck, messing with our electrical outlets.  I grabbed a pistol and looked out the window without letting them know I was there.  Sure enough, two Mexican men in white T-shirts plugging a camera in on our deck.  The deck was our property and my father is the association president, he didn't even know about these guys.  My mom called the cops and the cops asked them who the hell they were and told them to stay off of people's property without authorization.  The cops hung around the area for a little while, too, until the guys left.  Turns out they were repairmen, they were here to repair shingles and roofing, and they had the video camera so they could document their work.  Their truck had no markings, and just having a truck or van with a ladder on the side doesn't automatically mean a contractor.  My dad was rather annoyed over it because the management company had apparently sent these guys out without telling the association or any of the homeowners.  Lots of BG's put ladders and stuff on their vehicles as camouflage, because then anybody who sees the vehicle will write it off as maintenance personnel or a contractor.  Most reputable contractors have marked vehicles with a phone number on the side that you can call if you're wondering what's going on and/or guys in a uniform with some kind of ID.  I believe your landlord did violate part of the lease agreement.  They're supposed to inform you ahead of time.  It goes along with how a landlord can't just randomly decide to walk into the house/apartment anytime they want.  They have to give you notice.  If I were you, I'd document this and ask your landlord about it, pointing out what's in the agreement.  Also, use it as a ace up your sleeve in case the landlord gets stupid with you in the future.    This stuff happens often enough, but they are legally required to give you 24-hour written notice, and that applies to every state that I know of.  I live in an apartment in MD and I know it applies where I live.  I admit I am confused by "I heard the front door opening" and then "I hear knocking on the door".  Was he in the house before he knocked or what ?  

"I need to replace the air filter upstairs."

In some cities, landlords are required by law to replace air filters as an energy conservation measure.

they were here to repair shingles and roofing

Since water leaks will damage the owner's property, and it doesn't take much water to cause thousands of dollars worth of damage, with the property I manage, you will never get a 24 hour warning call.  I will protect the owner's property rather than waiting.  I'm not aware of any law in any state the will prevent a property owner from protecting their property against water damage.z

Quoted: "I need to replace the air filter upstairs." In some cities, landlords are required by law to replace air filters as an energy conservation measure. they were here to repair shingles and roofing Since water leaks will damage the owner's property, and it doesn't take much water to cause thousands of dollars worth of damage, with the property I manage, you will never get a 24 hour warning call.  I will protect the owner's property rather than waiting.  I'm not aware of any law in any state the will prevent a property owner from protecting their property against water damage.z

Yeah, in my case, we were the homeowners (we owned the house itself, the deck and the roof).  It was just the management company not doing what they were supposed to do.  The association handled the issue with the management company and they were sure to notify the homeowners in writing from then on.  

OK let me answer the questions posed to  me:
1: You need to calm down a bit, or is every person that knocks on your door in lethal danger?
(from brickeye)

A: Short answer: NO (Only the ones who try to come IN that door without my OK).  What would you've done?  Let the guy waltz right in?  I explained that I was sound asleep "IF/when " this guy rang the doorbell and awoke to my startled and defencive dog and heard the door opening.   I maintained a DEFENCIVE posture until I was  SURE (which I never was) of the situation.  

2: Was he in the house before he knocked or what ? (by Bob1984)

A:  What I figure happened was this; He rang the doorbell/knocked and tried to come in.  He must have heard Jake bark or maybe my footsteps  when I bolted out of bed (the Front door is directly underneath the bedroom door and stairwell) and knocked on the door to make sure anyone was home.

3: In some cities, landlords are required by law to replace air filters as an energy conservation measure. (By zoom.  Not really a question I know but needs clarification)

A:  That does not constitute an EMERGENCY REPAIR  necessary for an "unannounced entry".  Your second example however does meet the criteria.

I did talk to the landlord and she said He was new and DID NOT make the 24 hour written notice.  She said she would talk to him and remind him of the lease agreements.

Quoted: OK let me answer the questions posed to  me: 1: You need to calm down a bit, or is every person that knocks on your door in lethal danger? (from brickeye) A: Short answer: NO (Only the ones who try to come IN that door without my OK).  What would you've done?  Let the guy waltz right in?  I explained that I was sound asleep "IF/when " this guy rang the doorbell and awoke to my startled and defencive dog and heard the door opening.   I maintained a DEFENCIVE posture until I was  SURE (which I never was) of the situation.   2: Was he in the house before he knocked or what ? (by Bob1984) A:  What I figure happened was this; He rang the doorbell/knocked and tried to come in.  He must have heard Jake bark or maybe my footsteps  when I bolted out of bed (the Front door is directly underneath the bedroom door and stairwell) and knocked on the door to make sure anyone was home. 3: In some cities, landlords are required by law to replace air filters as an energy conservation measure. (By zoom.  Not really a question I know but needs clarification) A:  That does not constitute an EMERGENCY REPAIR  necessary for an "unannounced entry".  Your second example however does meet the criteria. I did talk to the landlord and she said He was new and DID NOT make the 24 hour written notice.  She said she would talk to him and remind him of the lease agreements.

Thanks for the clarification I think you did good.  

I have had a landlord and a repair man receive the business end of a firearm because they entered unannounced.  

Unannounced =
1 no prior letter/phonecall +
2. unsolicited entry into my house with/without knocking first +
3. failure to verbally announce presence (clearly and loudly)

If someone comes into my (leased) home unannounced and uninvited they can expect to be met with a firearm and one hell of a scolding afterwards. As tennants we have secured the right to use the premises as if we owned it and are subject to the security and privacy rights that accompany ownership (unless one of us is STUPID enough to sign a lease that has an unannounced repairs clause within it)

Quoted: I have had a landlord and a repair man receive the business end of a firearm because they entered unannounced.   Unannounced = 1 no prior letter/phonecall + 2. unsolicited entry into my house with/without knocking first + 3. failure to verbally announce presence (clearly and loudly) If someone comes into my (leased) home unannounced and uninvited they can expect to be met with a firearm and one hell of a scolding afterwards. As tennants we have secured the right to use the premises as if we owned it and are subject to the security and privacy rights that accompany ownership (unless one of us is STUPID enough to sign a lease that has an unannounced repairs clause within it)

And even then, a lot of states/jurisdictions have it in law that a landlord must inform you of any repairs/inspections no matter what the lease says.  Unannounced repairs/inpsections are bad juju for any landlord.  

I ended up pointing a 12ga at a "maintenance guy" who walked right on into my apt, while I was in the tub. He didn't say hello, call out to ask if anyone was home, etc. Walked in like he owned the place. He about shit himself when I rounded the corner, naked, with a 12ga. Claimed to be there to check something. Yeah, bull.

Told the managment about the incident, they knew nothing about it.  I told them they'd damned best let me know before someone came over again, lest he have a gun stuck in his face or worse.

Guy was later busted stealing from tenants when they weren't home. Gee, who'd have thunk it?

I would have a hard time living where some stranger could just walk in any time they felt like it.