I have a nice book that a friend from Florida sent me. It has many wishers and I posted it. Someone did request it with the following conditions;

Will not accept books if they are currently in a smoking home, they have been around cats and dogs, ex-library books, that has been in a damp environment or yellow or stain. it isn't yellowed or stained, I have a non smoking home, but I have a black lab. Also, my friend has a cat. The book looks brand new, no smell etc. I want to  say this doesn't meet conditions because of my lab and her cat. Will it be held against me at PBS if I don't send it? Should I PM them and explain why I don't feel comfortable sending it?

Also, I have read that WL books are timing out and going through several people and other members have said that helps find inactive accounts? What does that mean?

Thanks in advance, I'm worried about the requester of that one book especially if his/her reasoning is allergies. Then I definitely don't want to send it!

Since your book doesn't meet the condition due to pets just decline and it will be offered to the next in line. It will not go against you and the requestor will be glad you didn't send a book that violated their RC.

ETA: It doesn't matter the requestor's reasoning for not wanting a book that was near animals. If you cannot meet the condition set you just say does not meet RC.

Books time out when someone does not respond either to mail out a book or accept a book offered in so many days. After this happens x amount of times the account gets reviewed and dormant accounts get closed.

I don't let my books be around my cats or dog if I can help it but the RC is really clear that if you have a cat or a dog, they don't want your book.  They're probably allergic to pet dander or something which is everywhere when you have a pet.

Should I PM them and explain

You can't PM someone until you have accepted their Requestor Condition. That is, you don't know the user that has the RC until you have said yes and if you say no, it will not show you the user name. When you say no, it will ask you to give a reason and you can just say
"Pets". Then the next person in line will be offered the book. They may have an RC as well. Just keep going until you get an RC that you can meet or a request with no RC. Rejecting an RC will not be held against you in anyway. Don't be rude in the reason box, but do put something in there.

Inactive users are users who have stopped using the site but have not closed their accounts. If they are offered a book and don't come on to say "Yes, I want this book!" within 48 hours, the book goes to the next person. If that happens to one account several times in a row (we don't know exactly how many, more than one for sure), the account may be marked as inactive and taken out of line for other books. This is usually only an issue for wishlisted books, especially the ones with slower, longer lines. People get tired of waiting and just abandon their accounts.

PBS set up the RCs that we can decline them without any repercussions.  The person cannot contact us.  We cannot contact them, other than the little box to explain the reason.  This is one of the very few orders that do not end up in the Transaction Archive.  This is to protect us.  We can turn down an RC without concerns, as long as we are polite.

(PBS can see both sides.  They can respond to reported rude reasons.)

Emily said it well. If you turn down a request because of the RC, this is done anonymously for both parties, the sender and the requestor.

If you want to send a PM to a requestor about their RC, you must first accept the request to find out who to send a PM to. Although sending a PM to clarify a requestor's RC can be helpful in some situations, it can also result in complications or continued uncertainty and should probably be used sparingly. After contacting a requestor either party may still cancel the request, so it is not yet a done deal if you have accepted a request simply to contact the requestor to ask about their RC. If you are uncertain about an RC, however, it is often best to decline it, even though the system does allow you to accept a request and contact the requestor if you wish to do so.

I get a number of cozies from a friend who smokes so whenever there's an RC about that I decline, even though I can't smell anything. There's no smoking in our house and it may be a while since she gave me the books but some people have a much more sensitive sense of smell than I do.

I just felt bad, there were 67 wishers and I'm sure this person was waiting a long time for this. I appreciate all the advice, it was most helpful!

I read somewhere some members stay #1 on the wl because their RC is difficult to meet and it gets declined.  

They have decided they want a very high level of purity that resembles buying the book new at the store.  

That's their choice, which is good.  Many people behind them would LOVE  to have your book!

Kind of a side issue, but I really wouldn't take the issues posted on this forum as the average experience. The average swap goes off without a hitch. People only post here when there is an issue. Even if you see two or three people posting about WL books timing out, you're just getting a self selected sample of people who are having this particular problem. The vast majority of swappers are not, so unless you encounter this problem, I wouldn't really worry about it.

As others have said - people with outrageous requests for popular books tend to congregate at the top, as sender after sender skips over them. 

The person with the RCs doesn't lose their place in line.  They stay #1 on the WL and are offered the next copy posted.

Now, they may get passed over several times until someone posts a book that meets their requirements but that's on them and their RC.

People with RCs understand that there is a possibility that they will wait a little longer than average for a book.

I am not sure her real question was answered: "Will it be held against me at PBS if I don't send it? Should I PM them and explain why I don't feel comfortable sending it?"    There is nothing negative by PBS about turning down any RC.  You don't have to state a reason to anyone.  In the box that pops up, I type two letters:  OK.    Many people, including myself, turn down 80-90% of all RC conditions, most of which I don't even read if they have more than a dozen words.

Actually, PBS is rather firm that they want an answer.  There is no negative response to turning it down.  But a blank answer can get a reaction from PBS.  I strongly recommend using something more in line with "Does not meet". 

 Many people, including myself, turn down 80-90% of all RC conditions, most of which I don't even read if they have more than a dozen words.

I have an RC and my experience is that most people do not turn them down for no particular reason. In fact, hardly anyone does.

Having said that. there is no penalty for turning down RCs ... that's why there is a "Cancel Order" button and a "Cannot Mail" button and a "Does Not Meet RCs" button .. they are there to use when needed.

PBS does recommend being polite when a RC is turned down, or a book cannot be mailed for whatever reason. You are not sending a message to PBS (although PBS can see them if needed) when you fill in those boxes, you are sending a message directly to the book requestor and if a message is rude, they may very well complain to PBS. (Not that I think you would send a rude message, just a point of info!)

There is really no point to contacting PBS about routine book transactions that they have provided methods to handle already, like a cancel button. There are more than 25,000 books mailed per week here, and nobody from PBS is monitoring trades or message sent between users unless they are asked to do so via a user complaint.