Understanding Restricted-Entry Intervals for Pesticides

A restricted-entry interval (REI) is the period of time that agricultural workers, or anyone else, must not do hand labour in treated areas after a pesticide has been applied. This is to allow residues and vapours to dissipate to safe levels for work to be performed. An REI can range from 12 hours to several days. The pesticide label may specify a number of REIs depending on crop or worker activity. Complying with REI directions is a legal requirement and part of pesticide safety.

Hand labour tasks involve worker contact with treated surfaces such as plants, plant parts, or soil. Activities can include harvesting, detasseling, thinning, weeding, scouting, planting, mowing, etc. Agricultural employers have a responsibility to ensure that agricultural workers and others on site are aware of any REIs in effect, and that everyone remains outside treated areas until the interval period ends.

Schedule pesticide applications and worker tasks to respect restricted-entry intervals.

Between 4-12 hours after pesticide application:

A certified applicator may enter a treated area during the REI period to perform short-term tasks provided

• No entry until after 4 hours and no hand labour activity is performed
• The certified applicator must wear PPE as specified on the pesticide label for mixers/loaders and wear a NIOSH-approved respirator. The agricultural employer must ensure protective equipment is worn and used correctly
• The time in the treated area must not exceed 1 hour in any 24-hour period

12 hours after pesticide application:

• Workers and others must not enter the affected area for 12 hours after application
• For REIs longer than 12 hours, people may enter after 12 hours, but must not contact surfaces likely to have residue
• No hand labour can be performed until the REI period ends
• PPE not required unless specified on the label 

Examples of Entry Situations Prior to REI Ending

Certified Applicators

• Assessing spray coverage
• Operating, moving, or repairing non-application field equipment such as irrigation equipment (with the exception of hand-set irrigation equipment), weather monitoring equipment and frost protection equipment

Workers and others

• A worker in a vehicle (e.g. open or closed-cab tractor, truck) may drive, or a worker may walk on roads, aisles, footpaths, or other pathways through the treated area. The route must ensure plants or other treated surfaces don’t brush against the worker and pesticide residues won’t drip on them
• After a pesticide application that is incorporated or injected into the soil, a worker may do tasks that don’t involve touching or disrupting the soil subsurface

Questions and Answers on REI

What do I do if the instructions on the pesticide label do not include an REI?

If a pesticide label’s use instructions don’t include an REI, apply a 12-hour minimum REI before anyone can enter a treated area for hand labour tasks (such as harvesting a crop). 

Why is the minimum REI 12 hours?

REIs protect workers, and others, from risks that may occur from both immediate and longer-term exposure to pesticide residues, vapours and particulates. A minimum 12-hour REI allows residues to dry and vapours to dissipate, limiting potential effects such as irritation or allergic reactions.

Do REIs apply to all pesticides?

Unless specified on the label, REIs do not apply to biopesticides such as microbials, pheromones, and other semiochemicals and non-conventional pesticides.

If it starts raining following pesticide application, can I reduce the REI? And what if I use application rates below those found on the product’s label, or apply pesticides in bands?

Any situation that would allow you to reduce the REI will be identified on the product label. If a specific REI does not apply to all hand labour activities, the label will identify different REIs for different tasks. Not respecting the stated intervals on pesticide labels could constitute a health risk and is, therefore, prohibited.

What can I do if I have to go back in a treated field before the REI has passed?

Every effort should be made to schedule pesticide applications to avoid early entry into treated areas. Examples of entry situations prior to REI ending are provided in tables 1 and 2. 

What do I do when the REI is 12 hours and the PHI is 0 days?

Entry is not permitted until after 12 hours.

What do I do when the PHI is different from the REI for harvesting?

REIs apply to hand labour tasks. Therefore for hand harvesting, follow the longer of the two intervals. Mechanical harvesting could occur at the PHI provided there is no worker contact with treated surfaces. 

If I apply more than one pesticides that have different PHI or REI entry intervals at the same time (in a tank mix), which interval do I choose?

To avoid harmful levels of pesticide residues while working in a treated field, you must always choose the longest REI found on the labels of all the pesticides that were used.

How is an REI different from a PHI?

The main difference between an REI (Restricted-Entry Interval) and a PHI (Preharvest Interval), is that the REI is the amount of time between the application of the pesticide and when workers can  enter to do hand labour tasks on the crops. The PHI is the minimum amount of time between the last application of a pesticide and when the crop can  be harvested.

Be sure to read and follow the pesticide label in order to always respect both the REI and the PHI.

More questions? Contact us at the Pest Management Information Service

1-800-267-6315 or pmra.info-arla@hc-sc.gc.ca