At What AQI Should You Stay Indoors?

At What AQI Should You Stay Indoors on the North Shore?

The Air Quality Index (AQI) scale runs from 0 to 500, and most health authorities recommend limiting outdoor activity once AQI reaches 101 (Unhealthy for Sensitive Groups) and staying indoors entirely when it hits 151 or higher. For residents in North Vancouver, West Vancouver, and surrounding North Shore communities, wildfire smoke and seasonal weather can push local AQI into hazardous territory, making indoor air quality a serious home health issue.

Wildfire seasons have been getting longer and more intense across British Columbia, and the North Shore is not insulated from the effects. Smoke drifts down from Interior wildfires, marine air stagnates under inversions, and older homes trap pollutants indoors. Knowing where the AQI thresholds sit and what they mean for your family’s health is the first step. Understanding what your home is doing to protect or expose you is the second.

Key Takeaways

An AQI of 0–50 is considered Good, and 51–100 is Moderate. Most healthy adults can continue normal outdoor activity in these ranges.
At AQI 101–150 (Unhealthy for Sensitive Groups), children, seniors, and anyone with respiratory or heart conditions should move activities indoors.
At AQI 151 and above, everyone should stay indoors and keep windows closed, regardless of health status.
Staying indoors only helps if your home’s air is actually clean. Leaky building envelopes, poor ventilation, and aging HVAC systems can make indoor air worse than outdoor air on a low-AQI day.
Renovation projects that improve airtightness, insulation, and mechanical ventilation directly upgrade how well your home performs as a refuge during poor air quality events.

Understanding the AQI Scale: What Each Level Means

The AQI is a standardized scale used across North America to communicate how polluted outdoor air is on any given day. In Canada, the equivalent metric is the Air Quality Health Index (AQHI), which runs from 1 to 10+ rather than 0 to 500, but the underlying logic is the same: the higher the number, the greater the health risk.

Here is how the US EPA’s AQI categories break down, which are widely referenced in Canadian public health guidance as well:

AQI Range	Category	Who Is at Risk	Recommended Action
0–50	Good	No one at significant risk	Normal outdoor activity is fine
51–100	Moderate	Unusually sensitive individuals	Sensitive groups should consider limiting prolonged outdoor exertion
101–150	Unhealthy for Sensitive Groups	Children, seniors, asthma/heart patients	Sensitive groups stay indoors; others limit extended outdoor activity
151–200	Unhealthy	Everyone	Everyone should reduce outdoor exertion and stay inside when possible
201–300	Very Unhealthy	Everyone, serious health effects	Stay indoors, keep windows sealed, run air filtration
301–500	Hazardous	Emergency conditions for all	Do not go outside; take all protective measures indoors

The short answer: for sensitive groups, 101 is the threshold. For everyone else, 151 is the number to watch. Above 200, there is no safe level of prolonged outdoor exposure for any healthy adult.

Things You Must Know

1. Staying Indoors Only Helps If Your Home Can Actually Filter Incoming Air

Many North Shore homes, particularly those built before the 1990s, have significant air leakage through the building envelope. During a wildfire smoke event, fine particulate matter (PM2.5) infiltrates through gaps in windows, doors, and unsealed penetrations. Closing your windows reduces exposure, but it does not eliminate it unless your home is reasonably airtight and running a properly maintained HVAC or ventilation system with a quality filter. A professional indoor air quality test for your home on the North Shore can reveal exactly how much outdoor pollution is getting in and where it is entering.

2. Your HVAC Filter Rating Matters More Than You Think

Standard HVAC filters are rated using the MERV scale. A MERV 8 filter catches large dust particles but allows fine wildfire smoke particulates to pass through freely. During an AQI event above 150, you ideally want a MERV 13 filter or better, or a standalone HEPA air purifier in key living areas. Upgrading your HVAC system as part of a larger home renovation is one of the most practical ways to meaningfully improve your home’s ability to protect your family year-round.

3. Indoor Pollutants Can Stack on Top of Outdoor Ones

If your home has moisture problems, off-gassing from older building materials, or inadequate exhaust ventilation in kitchens and bathrooms, indoor pollution levels can actually exceed outdoor levels even on moderate AQI days. Sealing out outdoor air without addressing internal sources does not solve the problem. A whole-home renovation approach that addresses the building envelope, ventilation, and materials together is the most effective path forward.

What Makes North Shore Air Quality Different?

The North Shore sits between Burrard Inlet and the Coast Mountains, a geography that creates predictable air quality challenges. Temperature inversions during summer trap smoke and pollutants in the valley below the mountain ridgeline. When BC Interior wildfires are active, that smoke settles over North Vancouver and West Vancouver with very little wind to clear it.

Communities like Lynn Valley, Deep Cove, Upper Lonsdale, and Edgemont are especially susceptible to trapped smoke events because of their elevation profiles and tree canopy, which can limit natural air circulation at street level. West Vancouver properties along the upper slopes may sit above an inversion layer on some days, but ground-level areas along Marine Drive and lower North Vancouver can see significantly elevated particulate counts during active fire seasons.

How Does AQI Affect the Decision to Stay Indoors Day-to-Day?

Knowing the threshold is one thing. Applying it practically is another. Here is a realistic framework for how North Shore families can use AQI readings in daily decisions:

Check your local AQI before planning outdoor activity. BC’s AirCare, IQAir, and Environment and Climate Change Canada all publish real-time readings. North Shore residents should bookmark a source that shows granular local data rather than Metro Vancouver averages, which can underreport conditions in specific valleys.
Identify your household’s sensitive individuals. Children under 12, adults over 65, and anyone with asthma, COPD, or cardiovascular conditions should apply the 101 threshold, not the 151 threshold. Their lungs work harder to filter particulates that healthy adults can handle more easily.
Prepare your indoor environment before AQI rises. During clear days, ensure HVAC filters are fresh, HEPA purifiers are positioned in bedrooms and main living areas, and any fresh-air intake dampers on your ventilation system can be shut manually or automatically during smoke events.
Reduce internal combustion sources indoors. Gas stoves, candles, and wood-burning fireplaces add indoor particulate load on top of whatever is infiltrating from outside. On high-AQI days, switching to electric cooking and eliminating combustion sources inside the home meaningfully reduces total exposure.
Monitor your home’s air directly. Consumer-grade indoor air quality monitors have become significantly more accurate and affordable. Placing one in your main living area and one in a bedroom gives you real data on whether your home’s defenses are working during a smoke event.

When Is Outdoor AQI “Bad Enough” to Affect People Who Feel Fine?

Research suggests that healthy adults begin experiencing measurable lung function changes at AQI levels around 150, even when they report feeling normal. Symptoms like scratchy throat, mild eye irritation, or unexplained fatigue during outdoor activity at moderate-to-high AQI are often dismissed as unrelated but may be direct physiological responses to PM2.5 exposure.

The insidious quality of fine particulate pollution is that it does not always produce immediate, obvious symptoms. This is especially true for younger, healthier adults who may not notice the incremental lung burden from repeated exposure to AQI levels in the 100–150 range across a full wildfire season.

Studies on cumulative PM2.5 exposure link repeated seasonal smoke events to increased rates of cardiovascular and respiratory illness over multi-year periods, not just during individual high-AQI days. Long-term exposure to even moderate particulate levels has been associated with reduced lung capacity in otherwise healthy adults.

How Can a Home Renovation Improve Your Protection During Poor Air Quality Events?

This is where the conversation becomes directly relevant for North Shore homeowners who are planning major renovations or home additions. A home that performs well during wildfire season is not an accident. It is a product of intentional building decisions made during design and construction.

Renovation Upgrade	Air Quality Benefit	Additional Home Benefit
Building envelope improvements (insulation, air sealing)	Significantly reduces smoke infiltration during AQI events	Reduced heating and cooling costs year-round
Modern HVAC with MERV 13+ filtration	Filters fine particulates from circulated air	Year-round comfort, humidity control
Heat Recovery Ventilator (HRV) with bypass mode	Allows fresh air exchange in clean-air conditions; can be bypassed during smoke events	Reduces indoor CO2 buildup, improves sleep quality
Window and door replacement	Eliminates major infiltration pathways for outdoor smoke	Noise reduction, improved thermal comfort
Low-VOC and non-toxic interior finishes	Reduces indoor pollutant baseline so outdoor events do not compound existing problems	Healthier indoor environment year-round

For homeowners on the North Shore planning larger-scale renovations, these upgrades are most cost-effective when integrated into a comprehensive project rather than addressed piecemeal later. If you are renovating a whole floor, adding an addition, or doing a structural project, this is the time to address the building envelope and mechanical systems simultaneously. Understanding how a home renovation can improve indoor air quality and wellness on the North Shore helps homeowners see how construction decisions connect directly to long-term health outcomes.

Common Mistakes Homeowners Make During High-AQI Events

Assuming “staying inside” is enough without sealing the home. Simply closing windows in a drafty older home still allows significant smoke infiltration through gaps in the building envelope.
Running exhaust fans continuously. Bathroom and kitchen exhaust fans depressurize the home and actively pull outdoor air (and smoke) in through any available gap. Use them only when needed during smoke events.
Relying on a box fan without a filter. A box fan alone moves air but does not filter it. Attaching a MERV 13 filter to a box fan is a widely recommended low-cost solution for temporary smoke protection in rooms without HVAC coverage.
Using a wood-burning fireplace during a smoke event. This adds combustion particulates to an already compromised indoor air environment.
Waiting until AQI is hazardous to take action. Preparation done before AQI spikes (clean filters in place, purifiers running, dampers identified) is far more effective than scrambling when smoke is already thick outside.
Not checking whether their HVAC system’s fresh air damper is open or closed. Many forced-air systems draw in outdoor air by default. During smoke events, that damper should be closed so the system recirculates and filters indoor air only.

Homeowners dealing with persistent indoor air quality concerns unrelated to seasonal smoke events may also want to look at the signs of poor indoor air quality on the North Shore to better understand whether their home has a structural or systemic problem that goes beyond seasonal AQI spikes.

Frequently Asked Questions

Can poor air quality cause heart palpitations?

Yes, there is a recognized link between elevated particulate pollution and cardiac symptoms including palpitations, irregular heartbeat, and increased heart rate. Fine particles (PM2.5) can enter the bloodstream through the lungs and trigger inflammatory responses that affect cardiovascular function. Individuals with pre-existing heart conditions are at greatest risk, but even healthy adults have reported cardiac symptoms during prolonged exposure to AQI levels above 150. If you experience palpitations during or after a high-AQI period, it is worth discussing with a physician, particularly if symptoms are new or recurring.

Can poor air quality cause dizziness?

Dizziness during high-AQI events is not uncommon and can result from reduced oxygen exchange efficiency in the lungs, inflammatory responses, or a drop in blood pressure triggered by particulate exposure. Carbon monoxide from combustion-based smoke can also accumulate indoors if ventilation is poor, which directly causes dizziness and headache. If indoor air quality in your home is consistently poor, that can produce dizziness and fatigue even on days when outdoor AQI is moderate. Understanding how bad indoor air quality can make you sick is an important step for any homeowner experiencing unexplained symptoms.

Can bad air quality cause chest tightness?

Chest tightness is one of the most commonly reported symptoms during wildfire smoke events and is a direct response to airway inflammation caused by inhaled fine particulates. It can occur in people with no prior diagnosis of asthma or respiratory disease. If chest tightness develops during or shortly after exposure to high-AQI outdoor air, moving indoors to a filtered environment should be the immediate step. Persistent or severe chest tightness requires medical attention, as it can also be a symptom of conditions unrelated to air quality.

What AQI is bad for asthma?

For people with asthma, health authorities generally recommend taking protective measures starting at AQI 101 (Unhealthy for Sensitive Groups). At this level, asthma triggers become significantly more likely during outdoor exertion. Above 150, even short outdoor exposure can provoke an asthmatic episode for individuals with moderate to severe asthma. The particle sizes most relevant to asthma are PM2.5 and PM10, both of which are captured in the overall AQI reading. Ensuring your home’s indoor air is properly filtered during smoke events is especially critical for asthmatic household members.

What is the 4-4-4 rule for asthma?

The 4-4-4 rule is a breathing technique sometimes taught to asthma patients to help manage mild symptoms and reduce anxiety during an episode: inhale for 4 counts, hold for 4 counts, and exhale for 4 counts, repeated several times. It is a relaxation and breath-control method, not a medical treatment, and it does not replace prescribed medication or emergency protocols. During an asthma episode triggered by poor air quality, the priority is to remove the person from the polluted environment, administer any prescribed reliever medication, and seek emergency medical care if symptoms do not improve quickly.

The Bottom Line for North Shore Homeowners

The AQI threshold for staying indoors is 101 for sensitive groups and 151 for everyone else. But that guidance assumes you have somewhere genuinely protective to go inside.

For many older homes across North Vancouver, West Vancouver, and other North Shore communities, the building envelope was never designed with wildfire smoke in mind. Air leaks freely through aging window seals, unsealed penetrations, and insufficiently insulated walls. Closing the front door during a smoke event is a start, but it is not a solution if your home cannot maintain a meaningfully cleaner indoor environment than what is outside.

Homeowners planning major renovations have a real opportunity to address this directly. Building envelope improvements, HVAC upgrades, and thoughtful material selection are not just comfort and efficiency investments. They are health investments with measurable, year-round impact. Choosing the right materials is part of this picture, and looking at the best healthy building materials for home renovation on the North Shore can help you understand what options support long-term indoor air quality.

Ready to Make Your North Shore Home Safer Year-Round?

Kennedy Construction has been building and renovating homes across the North Shore for over 20 years. Whether you are planning a large-scale whole-home renovation, a home addition, or a targeted building envelope upgrade, the team at Kennedy Construction understands how construction quality directly affects your home’s comfort, health, and long-term value.

With 8 HAVAN Awards and 1 Georgie Award, Kennedy Construction has earned a reputation for quality workmanship, transparent communication, and projects done right the first time. If you are a homeowner in North Vancouver, West Vancouver, or surrounding communities and you are ready to have a real conversation about what your home needs, reach out to the team directly.

Call Kennedy Construction: 604-986-3244