Laws don’t work unless most people comply with them voluntarily. This compliance is helped along by the understanding that violations of the law will be enforced and that the penalties are appropriate.

So, it’s good news that many landlords are trying to follow the law that requires them to test for radon in all buildings with rental units. But it’s not so good to find out that the state has no database of rental properties to know which ones are out of compliance, and that it’s still unclear what agencies will enforce the penalties. It is also not much comfort for tenants to find out that if their apartment is contaminated with radon, they’ll still have to sue the landlord to force remediation.

Since radon is the second-leading cause of lung cancer after tobacco, this confusion is no small matter. And considering that the law was passed five years ago, the state has had more than enough time to make a clear statement about its requirements and the consequences of breaking them.

Tenants should not be left wondering if the air in their apartments is contaminated, and they should be able to expect the state will stand behind them if it is.

Radon is a naturally occurring gas that seeps out of the ground when uranium decays. It is common in New England and often found in basements and private wells. It can be mitigated, however, if it is found through a test, which can be conducted with a kit that costs as little as $30.

When the radon law was passed in 2009, all buildings with rental apartments were supposed to be in compliance by 2012. But the next Legislature pushed the compliance date to this March 1. Some residents have been waiting five years to learn if they have radon in their apartments, and they face a lengthy enforcement process if they do.

Now, well past the deadline, staff members at the Division of Environmental Health in the Department of Health and Human Services say they are scrambling to keep up with the load of paperwork and requests for information that have been flooding in.

With five years to prepare for this deadline, it should have come as no surprise. With no clear message about who will enforce the law and the consequences that would result from violating it, the widespread voluntary compliance required to make the law work could fail to come together.

The law is already weak, and poor enforcement could ensure its failure. The state owes renters and landlords a much better effort.